fcb116bc43
725 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Eric W. Biederman
|
fcb116bc43 |
signal: Replace force_fatal_sig with force_exit_sig when in doubt
Recently to prevent issues with SECCOMP_RET_KILL and similar signals being changed before they are delivered SA_IMMUTABLE was added. Unfortunately this broke debuggers[1][2] which reasonably expect to be able to trap synchronous SIGTRAP and SIGSEGV even when the target process is not configured to handle those signals. Add force_exit_sig and use it instead of force_fatal_sig where historically the code has directly called do_exit. This has the implementation benefits of going through the signal exit path (including generating core dumps) without the danger of allowing userspace to ignore or change these signals. This avoids userspace regressions as older kernels exited with do_exit which debuggers also can not intercept. In the future is should be possible to improve the quality of implementation of the kernel by changing some of these force_exit_sig calls to force_fatal_sig. That can be done where it matters on a case-by-case basis with careful analysis. Reported-by: Kyle Huey <me@kylehuey.com> Reported-by: kernel test robot <oliver.sang@intel.com> [1] https://lkml.kernel.org/r/CAP045AoMY4xf8aC_4QU_-j7obuEPYgTcnQQP3Yxk=2X90jtpjw@mail.gmail.com [2] https://lkml.kernel.org/r/20211117150258.GB5403@xsang-OptiPlex-9020 Fixes: |
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Eric W. Biederman
|
e349d945fa |
signal: Don't always set SA_IMMUTABLE for forced signals
Recently to prevent issues with SECCOMP_RET_KILL and similar signals
being changed before they are delivered SA_IMMUTABLE was added.
Unfortunately this broke debuggers[1][2] which reasonably expect to be
able to trap synchronous SIGTRAP and SIGSEGV even when the target
process is not configured to handle those signals.
Update force_sig_to_task to support both the case when we can allow
the debugger to intercept and possibly ignore the signal and the case
when it is not safe to let userspace know about the signal until the
process has exited.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reported-by: Kyle Huey <me@kylehuey.com>
Reported-by: kernel test robot <oliver.sang@intel.com>
Cc: stable@vger.kernel.org
[1] https://lkml.kernel.org/r/CAP045AoMY4xf8aC_4QU_-j7obuEPYgTcnQQP3Yxk=2X90jtpjw@mail.gmail.com
[2] https://lkml.kernel.org/r/20211117150258.GB5403@xsang-OptiPlex-9020
Fixes:
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Linus Torvalds
|
5147da902e |
Merge branch 'exit-cleanups-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull exit cleanups from Eric Biederman: "While looking at some issues related to the exit path in the kernel I found several instances where the code is not using the existing abstractions properly. This set of changes introduces force_fatal_sig a way of sending a signal and not allowing it to be caught, and corrects the misuse of the existing abstractions that I found. A lot of the misuse of the existing abstractions are silly things such as doing something after calling a no return function, rolling BUG by hand, doing more work than necessary to terminate a kernel thread, or calling do_exit(SIGKILL) instead of calling force_sig(SIGKILL). In the review a deficiency in force_fatal_sig and force_sig_seccomp where ptrace or sigaction could prevent the delivery of the signal was found. I have added a change that adds SA_IMMUTABLE to change that makes it impossible to interrupt the delivery of those signals, and allows backporting to fix force_sig_seccomp And Arnd found an issue where a function passed to kthread_run had the wrong prototype, and after my cleanup was failing to build." * 'exit-cleanups-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (23 commits) soc: ti: fix wkup_m3_rproc_boot_thread return type signal: Add SA_IMMUTABLE to ensure forced siganls do not get changed signal: Replace force_sigsegv(SIGSEGV) with force_fatal_sig(SIGSEGV) exit/r8188eu: Replace the macro thread_exit with a simple return 0 exit/rtl8712: Replace the macro thread_exit with a simple return 0 exit/rtl8723bs: Replace the macro thread_exit with a simple return 0 signal/x86: In emulate_vsyscall force a signal instead of calling do_exit signal/sparc32: In setup_rt_frame and setup_fram use force_fatal_sig signal/sparc32: Exit with a fatal signal when try_to_clear_window_buffer fails exit/syscall_user_dispatch: Send ordinary signals on failure signal: Implement force_fatal_sig exit/kthread: Have kernel threads return instead of calling do_exit signal/s390: Use force_sigsegv in default_trap_handler signal/vm86_32: Properly send SIGSEGV when the vm86 state cannot be saved. signal/vm86_32: Replace open coded BUG_ON with an actual BUG_ON signal/sparc: In setup_tsb_params convert open coded BUG into BUG signal/powerpc: On swapcontext failure force SIGSEGV signal/sh: Use force_sig(SIGKILL) instead of do_group_exit(SIGKILL) signal/mips: Update (_save|_restore)_fp_context to fail with -EFAULT signal/sparc32: Remove unreachable do_exit in do_sparc_fault ... |
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Linus Torvalds
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a602285ac1 |
Merge branch 'per_signal_struct_coredumps-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull per signal_struct coredumps from Eric Biederman: "Current coredumps are mixed up with the exit code, the signal handling code, and the ptrace code making coredumps much more complicated than necessary and difficult to follow. This series of changes starts with ptrace_stop and cleans it up, making it easier to follow what is happening in ptrace_stop. Then cleans up the exec interactions with coredumps. Then cleans up the coredump interactions with exit. Finally the coredump interactions with the signal handling code is cleaned up. The first and last changes are bug fixes for minor bugs. I believe the fact that vfork followed by execve can kill the process the called vfork if exec fails is sufficient justification to change the userspace visible behavior. In previous discussions some of these changes were organized differently and individually appeared to make the code base worse. As currently written I believe they all stand on their own as cleanups and bug fixes. Which means that even if the worst should happen and the last change needs to be reverted for some unimaginable reason, the code base will still be improved. If the worst does not happen there are a more cleanups that can be made. Signals that generate coredumps can easily become eligible for short circuit delivery in complete_signal. The entire rendezvous for generating a coredump can move into get_signal. The function force_sig_info_to_task be written in a way that does not modify the signal handling state of the target task (because coredumps are eligible for short circuit delivery). Many of these future cleanups can be done another way but nothing so cleanly as if coredumps become per signal_struct" * 'per_signal_struct_coredumps-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: coredump: Limit coredumps to a single thread group coredump: Don't perform any cleanups before dumping core exit: Factor coredump_exit_mm out of exit_mm exec: Check for a pending fatal signal instead of core_state ptrace: Remove the unnecessary arguments from arch_ptrace_stop signal: Remove the bogus sigkill_pending in ptrace_stop |
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Eric W. Biederman
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00b06da29c |
signal: Add SA_IMMUTABLE to ensure forced siganls do not get changed
As Andy pointed out that there are races between
force_sig_info_to_task and sigaction[1] when force_sig_info_task. As
Kees discovered[2] ptrace is also able to change these signals.
In the case of seeccomp killing a process with a signal it is a
security violation to allow the signal to be caught or manipulated.
Solve this problem by introducing a new flag SA_IMMUTABLE that
prevents sigaction and ptrace from modifying these forced signals.
This flag is carefully made kernel internal so that no new ABI is
introduced.
Longer term I think this can be solved by guaranteeing short circuit
delivery of signals in this case. Unfortunately reliable and
guaranteed short circuit delivery of these signals is still a ways off
from being implemented, tested, and merged. So I have implemented a much
simpler alternative for now.
[1] https://lkml.kernel.org/r/b5d52d25-7bde-4030-a7b1-7c6f8ab90660@www.fastmail.com
[2] https://lkml.kernel.org/r/202110281136.5CE65399A7@keescook
Cc: stable@vger.kernel.org
Fixes:
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Linus Torvalds
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8cb1ae19bf |
x86/fpu updates:
- Cleanup of extable fixup handling to be more robust, which in turn
allows to make the FPU exception fixups more robust as well.
- Change the return code for signal frame related failures from explicit
error codes to a boolean fail/success as that's all what the calling
code evaluates.
- A large refactoring of the FPU code to prepare for adding AMX support:
- Distangle the public header maze and remove especially the misnomed
kitchen sink internal.h which is despite it's name included all over
the place.
- Add a proper abstraction for the register buffer storage (struct
fpstate) which allows to dynamically size the buffer at runtime by
flipping the pointer to the buffer container from the default
container which is embedded in task_struct::tread::fpu to a
dynamically allocated container with a larger register buffer.
- Convert the code over to the new fpstate mechanism.
- Consolidate the KVM FPU handling by moving the FPU related code into
the FPU core which removes the number of exports and avoids adding
even more export when AMX has to be supported in KVM. This also
removes duplicated code which was of course unnecessary different and
incomplete in the KVM copy.
- Simplify the KVM FPU buffer handling by utilizing the new fpstate
container and just switching the buffer pointer from the user space
buffer to the KVM guest buffer when entering vcpu_run() and flipping
it back when leaving the function. This cuts the memory requirements
of a vCPU for FPU buffers in half and avoids pointless memory copy
operations.
This also solves the so far unresolved problem of adding AMX support
because the current FPU buffer handling of KVM inflicted a circular
dependency between adding AMX support to the core and to KVM. With
the new scheme of switching fpstate AMX support can be added to the
core code without affecting KVM.
- Replace various variables with proper data structures so the extra
information required for adding dynamically enabled FPU features (AMX)
can be added in one place
- Add AMX (Advanved Matrix eXtensions) support (finally):
AMX is a large XSTATE component which is going to be available with
Saphire Rapids XEON CPUs. The feature comes with an extra MSR (MSR_XFD)
which allows to trap the (first) use of an AMX related instruction,
which has two benefits:
1) It allows the kernel to control access to the feature
2) It allows the kernel to dynamically allocate the large register
state buffer instead of burdening every task with the the extra 8K
or larger state storage.
It would have been great to gain this kind of control already with
AVX512.
The support comes with the following infrastructure components:
1) arch_prctl() to
- read the supported features (equivalent to XGETBV(0))
- read the permitted features for a task
- request permission for a dynamically enabled feature
Permission is granted per process, inherited on fork() and cleared
on exec(). The permission policy of the kernel is restricted to
sigaltstack size validation, but the syscall obviously allows
further restrictions via seccomp etc.
2) A stronger sigaltstack size validation for sys_sigaltstack(2) which
takes granted permissions and the potentially resulting larger
signal frame into account. This mechanism can also be used to
enforce factual sigaltstack validation independent of dynamic
features to help with finding potential victims of the 2K
sigaltstack size constant which is broken since AVX512 support was
added.
3) Exception handling for #NM traps to catch first use of a extended
feature via a new cause MSR. If the exception was caused by the use
of such a feature, the handler checks permission for that
feature. If permission has not been granted, the handler sends a
SIGILL like the #UD handler would do if the feature would have been
disabled in XCR0. If permission has been granted, then a new fpstate
which fits the larger buffer requirement is allocated.
In the unlikely case that this allocation fails, the handler sends
SIGSEGV to the task. That's not elegant, but unavoidable as the
other discussed options of preallocation or full per task
permissions come with their own set of horrors for kernel and/or
userspace. So this is the lesser of the evils and SIGSEGV caused by
unexpected memory allocation failures is not a fundamentally new
concept either.
When allocation succeeds, the fpstate properties are filled in to
reflect the extended feature set and the resulting sizes, the
fpu::fpstate pointer is updated accordingly and the trap is disarmed
for this task permanently.
4) Enumeration and size calculations
5) Trap switching via MSR_XFD
The XFD (eXtended Feature Disable) MSR is context switched with the
same life time rules as the FPU register state itself. The mechanism
is keyed off with a static key which is default disabled so !AMX
equipped CPUs have zero overhead. On AMX enabled CPUs the overhead
is limited by comparing the tasks XFD value with a per CPU shadow
variable to avoid redundant MSR writes. In case of switching from a
AMX using task to a non AMX using task or vice versa, the extra MSR
write is obviously inevitable.
All other places which need to be aware of the variable feature sets
and resulting variable sizes are not affected at all because they
retrieve the information (feature set, sizes) unconditonally from
the fpstate properties.
6) Enable the new AMX states
Note, this is relatively new code despite the fact that AMX support is in
the works for more than a year now.
The big refactoring of the FPU code, which allowed to do a proper
integration has been started exactly 3 weeks ago. Refactoring of the
existing FPU code and of the original AMX patches took a week and has
been subject to extensive review and testing. The only fallout which has
not been caught in review and testing right away was restricted to AMX
enabled systems, which is completely irrelevant for anyone outside Intel
and their early access program. There might be dragons lurking as usual,
but so far the fine grained refactoring has held up and eventual yet
undetected fallout is bisectable and should be easily addressable before
the 5.16 release. Famous last words...
Many thanks to Chang Bae and Dave Hansen for working hard on this and
also to the various test teams at Intel who reserved extra capacity to
follow the rapid development of this closely which provides the
confidence level required to offer this rather large update for inclusion
into 5.16-rc1.
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Merge tag 'x86-fpu-2021-11-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fpu updates from Thomas Gleixner:
- Cleanup of extable fixup handling to be more robust, which in turn
allows to make the FPU exception fixups more robust as well.
- Change the return code for signal frame related failures from
explicit error codes to a boolean fail/success as that's all what the
calling code evaluates.
- A large refactoring of the FPU code to prepare for adding AMX
support:
- Distangle the public header maze and remove especially the
misnomed kitchen sink internal.h which is despite it's name
included all over the place.
- Add a proper abstraction for the register buffer storage (struct
fpstate) which allows to dynamically size the buffer at runtime
by flipping the pointer to the buffer container from the default
container which is embedded in task_struct::tread::fpu to a
dynamically allocated container with a larger register buffer.
- Convert the code over to the new fpstate mechanism.
- Consolidate the KVM FPU handling by moving the FPU related code
into the FPU core which removes the number of exports and avoids
adding even more export when AMX has to be supported in KVM.
This also removes duplicated code which was of course
unnecessary different and incomplete in the KVM copy.
- Simplify the KVM FPU buffer handling by utilizing the new
fpstate container and just switching the buffer pointer from the
user space buffer to the KVM guest buffer when entering
vcpu_run() and flipping it back when leaving the function. This
cuts the memory requirements of a vCPU for FPU buffers in half
and avoids pointless memory copy operations.
This also solves the so far unresolved problem of adding AMX
support because the current FPU buffer handling of KVM inflicted
a circular dependency between adding AMX support to the core and
to KVM. With the new scheme of switching fpstate AMX support can
be added to the core code without affecting KVM.
- Replace various variables with proper data structures so the
extra information required for adding dynamically enabled FPU
features (AMX) can be added in one place
- Add AMX (Advanced Matrix eXtensions) support (finally):
AMX is a large XSTATE component which is going to be available with
Saphire Rapids XEON CPUs. The feature comes with an extra MSR
(MSR_XFD) which allows to trap the (first) use of an AMX related
instruction, which has two benefits:
1) It allows the kernel to control access to the feature
2) It allows the kernel to dynamically allocate the large register
state buffer instead of burdening every task with the the extra
8K or larger state storage.
It would have been great to gain this kind of control already with
AVX512.
The support comes with the following infrastructure components:
1) arch_prctl() to
- read the supported features (equivalent to XGETBV(0))
- read the permitted features for a task
- request permission for a dynamically enabled feature
Permission is granted per process, inherited on fork() and
cleared on exec(). The permission policy of the kernel is
restricted to sigaltstack size validation, but the syscall
obviously allows further restrictions via seccomp etc.
2) A stronger sigaltstack size validation for sys_sigaltstack(2)
which takes granted permissions and the potentially resulting
larger signal frame into account. This mechanism can also be used
to enforce factual sigaltstack validation independent of dynamic
features to help with finding potential victims of the 2K
sigaltstack size constant which is broken since AVX512 support
was added.
3) Exception handling for #NM traps to catch first use of a extended
feature via a new cause MSR. If the exception was caused by the
use of such a feature, the handler checks permission for that
feature. If permission has not been granted, the handler sends a
SIGILL like the #UD handler would do if the feature would have
been disabled in XCR0. If permission has been granted, then a new
fpstate which fits the larger buffer requirement is allocated.
In the unlikely case that this allocation fails, the handler
sends SIGSEGV to the task. That's not elegant, but unavoidable as
the other discussed options of preallocation or full per task
permissions come with their own set of horrors for kernel and/or
userspace. So this is the lesser of the evils and SIGSEGV caused
by unexpected memory allocation failures is not a fundamentally
new concept either.
When allocation succeeds, the fpstate properties are filled in to
reflect the extended feature set and the resulting sizes, the
fpu::fpstate pointer is updated accordingly and the trap is
disarmed for this task permanently.
4) Enumeration and size calculations
5) Trap switching via MSR_XFD
The XFD (eXtended Feature Disable) MSR is context switched with
the same life time rules as the FPU register state itself. The
mechanism is keyed off with a static key which is default
disabled so !AMX equipped CPUs have zero overhead. On AMX enabled
CPUs the overhead is limited by comparing the tasks XFD value
with a per CPU shadow variable to avoid redundant MSR writes. In
case of switching from a AMX using task to a non AMX using task
or vice versa, the extra MSR write is obviously inevitable.
All other places which need to be aware of the variable feature
sets and resulting variable sizes are not affected at all because
they retrieve the information (feature set, sizes) unconditonally
from the fpstate properties.
6) Enable the new AMX states
Note, this is relatively new code despite the fact that AMX support
is in the works for more than a year now.
The big refactoring of the FPU code, which allowed to do a proper
integration has been started exactly 3 weeks ago. Refactoring of the
existing FPU code and of the original AMX patches took a week and has
been subject to extensive review and testing. The only fallout which
has not been caught in review and testing right away was restricted
to AMX enabled systems, which is completely irrelevant for anyone
outside Intel and their early access program. There might be dragons
lurking as usual, but so far the fine grained refactoring has held up
and eventual yet undetected fallout is bisectable and should be
easily addressable before the 5.16 release. Famous last words...
Many thanks to Chang Bae and Dave Hansen for working hard on this and
also to the various test teams at Intel who reserved extra capacity
to follow the rapid development of this closely which provides the
confidence level required to offer this rather large update for
inclusion into 5.16-rc1
* tag 'x86-fpu-2021-11-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (110 commits)
Documentation/x86: Add documentation for using dynamic XSTATE features
x86/fpu: Include vmalloc.h for vzalloc()
selftests/x86/amx: Add context switch test
selftests/x86/amx: Add test cases for AMX state management
x86/fpu/amx: Enable the AMX feature in 64-bit mode
x86/fpu: Add XFD handling for dynamic states
x86/fpu: Calculate the default sizes independently
x86/fpu/amx: Define AMX state components and have it used for boot-time checks
x86/fpu/xstate: Prepare XSAVE feature table for gaps in state component numbers
x86/fpu/xstate: Add fpstate_realloc()/free()
x86/fpu/xstate: Add XFD #NM handler
x86/fpu: Update XFD state where required
x86/fpu: Add sanity checks for XFD
x86/fpu: Add XFD state to fpstate
x86/msr-index: Add MSRs for XFD
x86/cpufeatures: Add eXtended Feature Disabling (XFD) feature bit
x86/fpu: Reset permission and fpstate on exec()
x86/fpu: Prepare fpu_clone() for dynamically enabled features
x86/fpu/signal: Prepare for variable sigframe length
x86/signal: Use fpu::__state_user_size for sigalt stack validation
...
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Eric W. Biederman
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26d5badbcc |
signal: Implement force_fatal_sig
Add a simple helper force_fatal_sig that causes a signal to be delivered to a process as if the signal handler was set to SIG_DFL. Reimplement force_sigsegv based upon this new helper. This fixes force_sigsegv so that when it forces the default signal handler to be used the code now forces the signal to be unblocked as well. Reusing the tested logic in force_sig_info_to_task that was built for force_sig_seccomp this makes the implementation trivial. This is interesting both because it makes force_sigsegv simpler and because there are a couple of buggy places in the kernel that call do_exit(SIGILL) or do_exit(SIGSYS) because there is no straight forward way today for those places to simply force the exit of a process with the chosen signal. Creating force_fatal_sig allows those places to be implemented with normal signal exits. Link: https://lkml.kernel.org/r/20211020174406.17889-13-ebiederm@xmission.com Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> |
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Thomas Gleixner
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1bdda24c4a |
signal: Add an optional check for altstack size
New x86 FPU features will be very large, requiring ~10k of stack in signal handlers. These new features require a new approach called "dynamic features". The kernel currently tries to ensure that altstacks are reasonably sized. Right now, on x86, sys_sigaltstack() requires a size of >=2k. However, that 2k is a constant. Simply raising that 2k requirement to >10k for the new features would break existing apps which have a compiled-in size of 2k. Instead of universally enforcing a larger stack, prohibit a process from using dynamic features without properly-sized altstacks. This must be enforced in two places: * A dynamic feature can not be enabled without an large-enough altstack for each process thread. * Once a dynamic feature is enabled, any request to install a too-small altstack will be rejected The dynamic feature enabling code must examine each thread in a process to ensure that the altstacks are large enough. Add a new lock (sigaltstack_lock()) to ensure that threads can not race and change their altstack after being examined. Add the infrastructure in form of a config option and provide empty stubs for architectures which do not need dynamic altstack size checks. This implementation will be fleshed out for x86 in a future patch called x86/arch_prctl: Add controls for dynamic XSTATE components [dhansen: commit message. ] Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20211021225527.10184-2-chang.seok.bae@intel.com |
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Linus Torvalds
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9d235ac01f |
Merge branch 'ucount-fixes-for-v5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull ucounts fixes from Eric Biederman: "There has been one very hard to track down bug in the ucount code that we have been tracking since roughly v5.14 was released. Alex managed to find a reliable reproducer a few days ago and then I was able to instrument the code and figure out what the issue was. It turns out the sigqueue_alloc single atomic operation optimization did not play nicely with ucounts multiple level rlimits. It turned out that either sigqueue_alloc or sigqueue_free could be operating on multiple levels and trigger the conditions for the optimization on more than one level at the same time. To deal with that situation I have introduced inc_rlimit_get_ucounts and dec_rlimit_put_ucounts that just focuses on the optimization and the rlimit and ucount changes. While looking into the big bug I found I couple of other little issues so I am including those fixes here as well. When I have time I would very much like to dig into process ownership of the shared signal queue and see if we could pick a single owner for the entire queue so that all of the rlimits can count to that owner. That should entirely remove the need to call get_ucounts and put_ucounts in sigqueue_alloc and sigqueue_free. It is difficult because Linux unlike POSIX supports setuid that works on a single thread" * 'ucount-fixes-for-v5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: ucounts: Move get_ucounts from cred_alloc_blank to key_change_session_keyring ucounts: Proper error handling in set_cred_ucounts ucounts: Pair inc_rlimit_ucounts with dec_rlimit_ucoutns in commit_creds ucounts: Fix signal ucount refcounting |
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Eric W. Biederman
|
15bc01effe |
ucounts: Fix signal ucount refcounting
In commit |
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Eric W. Biederman
|
9230738308 |
coredump: Don't perform any cleanups before dumping core
Rename coredump_exit_mm to coredump_task_exit and call it from do_exit before PTRACE_EVENT_EXIT, and before any cleanup work for a task happens. This ensures that an accurate copy of the process can be captured in the coredump as no cleanup for the process happens before the coredump completes. This also ensures that PTRACE_EVENT_EXIT will not be visited by any thread until the coredump is complete. Add a new flag PF_POSTCOREDUMP so that tasks that have passed through coredump_task_exit can be recognized and ignored in zap_process. Now that all of the coredumping happens before exit_mm remove code to test for a coredump in progress from mm_release. Replace "may_ptrace_stop()" with a simple test of "current->ptrace". The other tests in may_ptrace_stop all concern avoiding stopping during a coredump. These tests are no longer necessary as it is now guaranteed that fatal_signal_pending will be set if the code enters ptrace_stop during a coredump. The code in ptrace_stop is guaranteed not to stop if fatal_signal_pending returns true. Until this change "ptrace_event(PTRACE_EVENT_EXIT)" could call ptrace_stop without fatal_signal_pending being true, as signals are dequeued in get_signal before calling do_exit. This is no longer an issue as "ptrace_event(PTRACE_EVENT_EXIT)" is no longer reached until after the coredump completes. Link: https://lkml.kernel.org/r/874kaax26c.fsf@disp2133 Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> |
||
|
Eric W. Biederman
|
4f627af8e6 |
ptrace: Remove the unnecessary arguments from arch_ptrace_stop
Both arch_ptrace_stop_needed and arch_ptrace_stop are called with an exit_code and a siginfo structure. Neither argument is used by any of the implementations so just remove the unneeded arguments. The two arechitectures that implement arch_ptrace_stop are ia64 and sparc. Both architectures flush their register stacks before a ptrace_stack so that all of the register information can be accessed by debuggers. As the question of if a register stack needs to be flushed is independent of why ptrace is stopping not needing arguments make sense. Cc: David Miller <davem@davemloft.net> Cc: sparclinux@vger.kernel.org Link: https://lkml.kernel.org/r/87lf3mx290.fsf@disp2133 Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> |
||
|
Eric W. Biederman
|
7d613f9f72 |
signal: Remove the bogus sigkill_pending in ptrace_stop
The existence of sigkill_pending is a little silly as it is functionally a duplicate of fatal_signal_pending that is used in exactly one place. Checking for pending fatal signals and returning early in ptrace_stop is actively harmful. It casues the ptrace_stop called by ptrace_signal to return early before setting current->exit_code. Later when ptrace_signal reads the signal number from current->exit_code is undefined, making it unpredictable what will happen. Instead rely on the fact that schedule will not sleep if there is a pending signal that can awaken a task. Removing the explict sigkill_pending test fixes fixes ptrace_signal when ptrace_stop does not stop because current->exit_code is always set to to signr. Cc: stable@vger.kernel.org Fixes: |
||
|
Linus Torvalds
|
14726903c8 |
Merge branch 'akpm' (patches from Andrew)
Merge misc updates from Andrew Morton: "173 patches. Subsystems affected by this series: ia64, ocfs2, block, and mm (debug, pagecache, gup, swap, shmem, memcg, selftests, pagemap, mremap, bootmem, sparsemem, vmalloc, kasan, pagealloc, memory-failure, hugetlb, userfaultfd, vmscan, compaction, mempolicy, memblock, oom-kill, migration, ksm, percpu, vmstat, and madvise)" * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (173 commits) mm/madvise: add MADV_WILLNEED to process_madvise() mm/vmstat: remove unneeded return value mm/vmstat: simplify the array size calculation mm/vmstat: correct some wrong comments mm/percpu,c: remove obsolete comments of pcpu_chunk_populated() selftests: vm: add COW time test for KSM pages selftests: vm: add KSM merging time test mm: KSM: fix data type selftests: vm: add KSM merging across nodes test selftests: vm: add KSM zero page merging test selftests: vm: add KSM unmerge test selftests: vm: add KSM merge test mm/migrate: correct kernel-doc notation mm: wire up syscall process_mrelease mm: introduce process_mrelease system call memblock: make memblock_find_in_range method private mm/mempolicy.c: use in_task() in mempolicy_slab_node() mm/mempolicy: unify the create() func for bind/interleave/prefer-many policies mm/mempolicy: advertise new MPOL_PREFERRED_MANY mm/hugetlb: add support for mempolicy MPOL_PREFERRED_MANY ... |
||
Vasily Averin
|
5f58c39819 |
memcg: enable accounting for signals
When a user send a signal to any another processes it forces the kernel to allocate memory for 'struct sigqueue' objects. The number of signals is limited by RLIMIT_SIGPENDING resource limit, but even the default settings allow each user to consume up to several megabytes of memory. It makes sense to account for these allocations to restrict the host's memory consumption from inside the memcg-limited container. Link: https://lkml.kernel.org/r/e34e958c-e785-712e-a62a-2c7b66c646c7@virtuozzo.com Signed-off-by: Vasily Averin <vvs@virtuozzo.com> Reviewed-by: Shakeel Butt <shakeelb@google.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Andrei Vagin <avagin@gmail.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Borislav Petkov <bp@suse.de> Cc: Christian Brauner <christian.brauner@ubuntu.com> Cc: Dmitry Safonov <0x7f454c46@gmail.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: "J. Bruce Fields" <bfields@fieldses.org> Cc: Jeff Layton <jlayton@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Jiri Slaby <jirislaby@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kirill Tkhai <ktkhai@virtuozzo.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Roman Gushchin <guro@fb.com> Cc: Serge Hallyn <serge@hallyn.com> Cc: Tejun Heo <tj@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Yutian Yang <nglaive@gmail.com> Cc: Zefan Li <lizefan.x@bytedance.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
||
|
Linus Torvalds
|
bcfeebbff3 |
Merge branch 'exit-cleanups-for-v5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull exit cleanups from Eric Biederman: "In preparation of doing something about PTRACE_EVENT_EXIT I have started cleaning up various pieces of code related to do_exit. Most of that code I did not manage to get tested and reviewed before the merge window opened but a handful of very useful cleanups are ready to be merged. The first change is simply the removal of the bdflush system call. The code has now been disabled long enough that even the oldest userspace working userspace setups anyone can find to test are fine with the bdflush system call being removed. Changing m68k fsp040_die to use force_sigsegv(SIGSEGV) instead of calling do_exit directly is interesting only in that it is nearly the most difficult of the incorrect uses of do_exit to remove. The change to the seccomp code to simply send a signal instead of calling do_coredump directly is a very nice little cleanup made possible by realizing the existing signal sending helpers were missing a little bit of functionality that is easy to provide" * 'exit-cleanups-for-v5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: signal/seccomp: Dump core when there is only one live thread signal/seccomp: Refactor seccomp signal and coredump generation signal/m68k: Use force_sigsegv(SIGSEGV) in fpsp040_die exit/bdflush: Remove the deprecated bdflush system call |
||
|
Linus Torvalds
|
48983701a1 |
Merge branch 'siginfo-si_trapno-for-v5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull siginfo si_trapno updates from Eric Biederman: "The full set of si_trapno changes was not appropriate as a fix for the newly added SIGTRAP TRAP_PERF, and so I postponed the rest of the related cleanups. This is the rest of the cleanups for si_trapno that reduces it from being a really weird arch special case that is expect to be always present (but isn't) on the architectures that support it to being yet another field in the _sigfault union of struct siginfo. The changes have been reviewed and marinated in linux-next. With the removal of this awkward special case new code (like SIGTRAP TRAP_PERF) that works across architectures should be easier to write and maintain" * 'siginfo-si_trapno-for-v5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: signal: Rename SIL_PERF_EVENT SIL_FAULT_PERF_EVENT for consistency signal: Verify the alignment and size of siginfo_t signal: Remove the generic __ARCH_SI_TRAPNO support signal/alpha: si_trapno is only used with SIGFPE and SIGTRAP TRAP_UNK signal/sparc: si_trapno is only used with SIGILL ILL_ILLTRP arm64: Add compile-time asserts for siginfo_t offsets arm: Add compile-time asserts for siginfo_t offsets sparc64: Add compile-time asserts for siginfo_t offsets |
||
|
Eric W. Biederman
|
307d522f5e |
signal/seccomp: Refactor seccomp signal and coredump generation
Factor out force_sig_seccomp from the seccomp signal generation and place it in kernel/signal.c. The function force_sig_seccomp takes a parameter force_coredump to indicate that the sigaction field should be reset to SIGDFL so that a coredump will be generated when the signal is delivered. force_sig_seccomp is then used to replace both seccomp_send_sigsys and seccomp_init_siginfo. force_sig_info_to_task gains an extra parameter to force using the default signal action. With this change seccomp is no longer a special case and there becomes exactly one place do_coredump is called from. Further it no longer becomes necessary for __seccomp_filter to call do_group_exit. Acked-by: Kees Cook <keescook@chromium.org> Link: https://lkml.kernel.org/r/87r1gr6qc4.fsf_-_@disp2133 Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> |
||
Frederic Weisbecker
|
a5dec9f82a |
posix-cpu-timers: Assert task sighand is locked while starting cputime counter
Starting the process wide cputime counter needs to be done in the same sighand locking sequence than actually arming the related timer otherwise this races against concurrent timers setting/expiring in the same threadgroup. Detecting that the cputime counter is started without holding the sighand lock is a first step toward debugging such situations. Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20210726125513.271824-2-frederic@kernel.org |
||
|
Eric W. Biederman
|
f4ac730234 |
signal: Rename SIL_PERF_EVENT SIL_FAULT_PERF_EVENT for consistency
It helps to know which part of the siginfo structure the siginfo_layout value is talking about. v1: https://lkml.kernel.org/r/m18s4zs7nu.fsf_-_@fess.ebiederm.org v2: https://lkml.kernel.org/r/20210505141101.11519-9-ebiederm@xmission.com Link: https://lkml.kernel.org/r/87zgumw8cc.fsf_-_@disp2133 Acked-by: Marco Elver <elver@google.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> |
||
|
Eric W. Biederman
|
c7fff9288d |
signal: Remove the generic __ARCH_SI_TRAPNO support
Now that __ARCH_SI_TRAPNO is no longer set by any architecture remove all of the code it enabled from the kernel. On alpha and sparc a more explict approach of using send_sig_fault_trapno or force_sig_fault_trapno in the very limited circumstances where si_trapno was set to a non-zero value. The generic support that is being removed always set si_trapno on all fault signals. With only SIGILL ILL_ILLTRAP on sparc and SIGFPE and SIGTRAP TRAP_UNK on alpla providing si_trapno values asking all senders of fault signals to provide an si_trapno value does not make sense. Making si_trapno an ordinary extension of the fault siginfo layout has enabled the architecture generic implementation of SIGTRAP TRAP_PERF, and enables other faulting signals to grow architecture generic senders as well. v1: https://lkml.kernel.org/r/m18s4zs7nu.fsf_-_@fess.ebiederm.org v2: https://lkml.kernel.org/r/20210505141101.11519-8-ebiederm@xmission.com Link: https://lkml.kernel.org/r/87bl73xx6x.fsf_-_@disp2133 Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> |
||
|
Eric W. Biederman
|
7de5f68d49 |
signal/alpha: si_trapno is only used with SIGFPE and SIGTRAP TRAP_UNK
While reviewing the signal handlers on alpha it became clear that si_trapno is only set to a non-zero value when sending SIGFPE and when sending SITGRAP with si_code TRAP_UNK. Add send_sig_fault_trapno and send SIGTRAP TRAP_UNK, and SIGFPE with it. Remove the define of __ARCH_SI_TRAPNO and remove the always zero si_trapno parameter from send_sig_fault and force_sig_fault. v1: https://lkml.kernel.org/r/m1eeers7q7.fsf_-_@fess.ebiederm.org v2: https://lkml.kernel.org/r/20210505141101.11519-7-ebiederm@xmission.com Link: https://lkml.kernel.org/r/87h7gvxx7l.fsf_-_@disp2133 Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> |
||
|
Eric W. Biederman
|
2c9f7eaf08 |
signal/sparc: si_trapno is only used with SIGILL ILL_ILLTRP
While reviewing the signal handlers on sparc it became clear that si_trapno is only set to a non-zero value when sending SIGILL with si_code ILL_ILLTRP. Add force_sig_fault_trapno and send SIGILL ILL_ILLTRP with it. Remove the define of __ARCH_SI_TRAPNO and remove the always zero si_trapno parameter from send_sig_fault and force_sig_fault. v1: https://lkml.kernel.org/r/m1eeers7q7.fsf_-_@fess.ebiederm.org v2: https://lkml.kernel.org/r/20210505141101.11519-7-ebiederm@xmission.com Link: https://lkml.kernel.org/r/87mtqnxx89.fsf_-_@disp2133 Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> |
||
Alexey Gladkov
|
f3791f4df5 |
Fix UCOUNT_RLIMIT_SIGPENDING counter leak
We must properly handle an errors when we increase the rlimit counter
and the ucounts reference counter. We have to this with RCU protection
to prevent possible use-after-free that could occur due to concurrent
put_cred_rcu().
The following reproducer triggers the problem:
$ cat testcase.sh
case "${STEP:-0}" in
0)
ulimit -Si 1
ulimit -Hi 1
STEP=1 unshare -rU "$0"
killall sleep
;;
1)
for i in 1 2 3 4 5; do unshare -rU sleep 5 & done
;;
esac
with the KASAN report being along the lines of
BUG: KASAN: use-after-free in put_ucounts+0x17/0xa0
Write of size 4 at addr ffff8880045f031c by task swapper/2/0
CPU: 2 PID: 0 Comm: swapper/2 Not tainted 5.13.0+ #19
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-alt4 04/01/2014
Call Trace:
<IRQ>
put_ucounts+0x17/0xa0
put_cred_rcu+0xd5/0x190
rcu_core+0x3bf/0xcb0
__do_softirq+0xe3/0x341
irq_exit_rcu+0xbe/0xe0
sysvec_apic_timer_interrupt+0x6a/0x90
</IRQ>
asm_sysvec_apic_timer_interrupt+0x12/0x20
default_idle_call+0x53/0x130
do_idle+0x311/0x3c0
cpu_startup_entry+0x14/0x20
secondary_startup_64_no_verify+0xc2/0xcb
Allocated by task 127:
kasan_save_stack+0x1b/0x40
__kasan_kmalloc+0x7c/0x90
alloc_ucounts+0x169/0x2b0
set_cred_ucounts+0xbb/0x170
ksys_unshare+0x24c/0x4e0
__x64_sys_unshare+0x16/0x20
do_syscall_64+0x37/0x70
entry_SYSCALL_64_after_hwframe+0x44/0xae
Freed by task 0:
kasan_save_stack+0x1b/0x40
kasan_set_track+0x1c/0x30
kasan_set_free_info+0x20/0x30
__kasan_slab_free+0xeb/0x120
kfree+0xaa/0x460
put_cred_rcu+0xd5/0x190
rcu_core+0x3bf/0xcb0
__do_softirq+0xe3/0x341
The buggy address belongs to the object at ffff8880045f0300
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 28 bytes inside of
192-byte region [ffff8880045f0300, ffff8880045f03c0)
The buggy address belongs to the page:
page:000000008de0a388 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8880045f0000 pfn:0x45f0
flags: 0x100000000000200(slab|node=0|zone=1)
raw: 0100000000000200 ffffea00000f4640 0000000a0000000a ffff888001042a00
raw: ffff8880045f0000 000000008010000d 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff8880045f0200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880045f0280: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff8880045f0300: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880045f0380: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff8880045f0400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
Disabling lock debugging due to kernel taint
Fixes:
|
||
|
Linus Torvalds
|
71bd934101 |
Merge branch 'akpm' (patches from Andrew)
Merge more updates from Andrew Morton: "190 patches. Subsystems affected by this patch series: mm (hugetlb, userfaultfd, vmscan, kconfig, proc, z3fold, zbud, ras, mempolicy, memblock, migration, thp, nommu, kconfig, madvise, memory-hotplug, zswap, zsmalloc, zram, cleanups, kfence, and hmm), procfs, sysctl, misc, core-kernel, lib, lz4, checkpatch, init, kprobes, nilfs2, hfs, signals, exec, kcov, selftests, compress/decompress, and ipc" * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (190 commits) ipc/util.c: use binary search for max_idx ipc/sem.c: use READ_ONCE()/WRITE_ONCE() for use_global_lock ipc: use kmalloc for msg_queue and shmid_kernel ipc sem: use kvmalloc for sem_undo allocation lib/decompressors: remove set but not used variabled 'level' selftests/vm/pkeys: exercise x86 XSAVE init state selftests/vm/pkeys: refill shadow register after implicit kernel write selftests/vm/pkeys: handle negative sys_pkey_alloc() return code selftests/vm/pkeys: fix alloc_random_pkey() to make it really, really random kcov: add __no_sanitize_coverage to fix noinstr for all architectures exec: remove checks in __register_bimfmt() x86: signal: don't do sas_ss_reset() until we are certain that sigframe won't be abandoned hfsplus: report create_date to kstat.btime hfsplus: remove unnecessary oom message nilfs2: remove redundant continue statement in a while-loop kprobes: remove duplicated strong free_insn_page in x86 and s390 init: print out unknown kernel parameters checkpatch: do not complain about positive return values starting with EPOLL checkpatch: improve the indented label test checkpatch: scripts/spdxcheck.py now requires python3 ... |
||
Al Viro
|
97c885d585 |
x86: signal: don't do sas_ss_reset() until we are certain that sigframe won't be abandoned
Currently we handle SS_AUTODISARM as soon as we have stored the altstack settings into sigframe - that's the point when we have set the things up for eventual sigreturn to restore the old settings. And if we manage to set the sigframe up (we are not done with that yet), everything's fine. However, in case of failure we end up with sigframe-to-be abandoned and SIGSEGV force-delivered. And in that case we end up with inconsistent rules - late failures have altstack reset, early ones do not. It's trivial to get consistent behaviour - just handle SS_AUTODISARM once we have set the sigframe up and are committed to entering the handler, i.e. in signal_delivered(). Link: https://lore.kernel.org/lkml/20200404170604.GN23230@ZenIV.linux.org.uk/ Link: https://github.com/ClangBuiltLinux/linux/issues/876 Link: https://lkml.kernel.org/r/20210422230846.1756380-1-ndesaulniers@google.com Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Acked-by: Oleg Nesterov <oleg@redhat.com> Tested-by: Nathan Chancellor <natechancellor@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
||
|
Linus Torvalds
|
c54b245d01 |
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull user namespace rlimit handling update from Eric Biederman: "This is the work mainly by Alexey Gladkov to limit rlimits to the rlimits of the user that created a user namespace, and to allow users to have stricter limits on the resources created within a user namespace." * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: cred: add missing return error code when set_cred_ucounts() failed ucounts: Silence warning in dec_rlimit_ucounts ucounts: Set ucount_max to the largest positive value the type can hold kselftests: Add test to check for rlimit changes in different user namespaces Reimplement RLIMIT_MEMLOCK on top of ucounts Reimplement RLIMIT_SIGPENDING on top of ucounts Reimplement RLIMIT_MSGQUEUE on top of ucounts Reimplement RLIMIT_NPROC on top of ucounts Use atomic_t for ucounts reference counting Add a reference to ucounts for each cred Increase size of ucounts to atomic_long_t |
||
|
Linus Torvalds
|
54a728dc5e |
Scheduler udpates for this cycle:
- Changes to core scheduling facilities:
- Add "Core Scheduling" via CONFIG_SCHED_CORE=y, which enables
coordinated scheduling across SMT siblings. This is a much
requested feature for cloud computing platforms, to allow
the flexible utilization of SMT siblings, without exposing
untrusted domains to information leaks & side channels, plus
to ensure more deterministic computing performance on SMT
systems used by heterogenous workloads.
There's new prctls to set core scheduling groups, which
allows more flexible management of workloads that can share
siblings.
- Fix task->state access anti-patterns that may result in missed
wakeups and rename it to ->__state in the process to catch new
abuses.
- Load-balancing changes:
- Tweak newidle_balance for fair-sched, to improve
'memcache'-like workloads.
- "Age" (decay) average idle time, to better track & improve workloads
such as 'tbench'.
- Fix & improve energy-aware (EAS) balancing logic & metrics.
- Fix & improve the uclamp metrics.
- Fix task migration (taskset) corner case on !CONFIG_CPUSET.
- Fix RT and deadline utilization tracking across policy changes
- Introduce a "burstable" CFS controller via cgroups, which allows
bursty CPU-bound workloads to borrow a bit against their future
quota to improve overall latencies & batching. Can be tweaked
via /sys/fs/cgroup/cpu/<X>/cpu.cfs_burst_us.
- Rework assymetric topology/capacity detection & handling.
- Scheduler statistics & tooling:
- Disable delayacct by default, but add a sysctl to enable
it at runtime if tooling needs it. Use static keys and
other optimizations to make it more palatable.
- Use sched_clock() in delayacct, instead of ktime_get_ns().
- Misc cleanups and fixes.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler udpates from Ingo Molnar:
- Changes to core scheduling facilities:
- Add "Core Scheduling" via CONFIG_SCHED_CORE=y, which enables
coordinated scheduling across SMT siblings. This is a much
requested feature for cloud computing platforms, to allow the
flexible utilization of SMT siblings, without exposing untrusted
domains to information leaks & side channels, plus to ensure more
deterministic computing performance on SMT systems used by
heterogenous workloads.
There are new prctls to set core scheduling groups, which allows
more flexible management of workloads that can share siblings.
- Fix task->state access anti-patterns that may result in missed
wakeups and rename it to ->__state in the process to catch new
abuses.
- Load-balancing changes:
- Tweak newidle_balance for fair-sched, to improve 'memcache'-like
workloads.
- "Age" (decay) average idle time, to better track & improve
workloads such as 'tbench'.
- Fix & improve energy-aware (EAS) balancing logic & metrics.
- Fix & improve the uclamp metrics.
- Fix task migration (taskset) corner case on !CONFIG_CPUSET.
- Fix RT and deadline utilization tracking across policy changes
- Introduce a "burstable" CFS controller via cgroups, which allows
bursty CPU-bound workloads to borrow a bit against their future
quota to improve overall latencies & batching. Can be tweaked via
/sys/fs/cgroup/cpu/<X>/cpu.cfs_burst_us.
- Rework assymetric topology/capacity detection & handling.
- Scheduler statistics & tooling:
- Disable delayacct by default, but add a sysctl to enable it at
runtime if tooling needs it. Use static keys and other
optimizations to make it more palatable.
- Use sched_clock() in delayacct, instead of ktime_get_ns().
- Misc cleanups and fixes.
* tag 'sched-core-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (72 commits)
sched/doc: Update the CPU capacity asymmetry bits
sched/topology: Rework CPU capacity asymmetry detection
sched/core: Introduce SD_ASYM_CPUCAPACITY_FULL sched_domain flag
psi: Fix race between psi_trigger_create/destroy
sched/fair: Introduce the burstable CFS controller
sched/uclamp: Fix uclamp_tg_restrict()
sched/rt: Fix Deadline utilization tracking during policy change
sched/rt: Fix RT utilization tracking during policy change
sched: Change task_struct::state
sched,arch: Remove unused TASK_STATE offsets
sched,timer: Use __set_current_state()
sched: Add get_current_state()
sched,perf,kvm: Fix preemption condition
sched: Introduce task_is_running()
sched: Unbreak wakeups
sched/fair: Age the average idle time
sched/cpufreq: Consider reduced CPU capacity in energy calculation
sched/fair: Take thermal pressure into account while estimating energy
thermal/cpufreq_cooling: Update offline CPUs per-cpu thermal_pressure
sched/fair: Return early from update_tg_cfs_load() if delta == 0
...
|
||
|
Linus Torvalds
|
b4b27b9eed |
Revert "signal: Allow tasks to cache one sigqueue struct"
This reverts commits |
||
|
Thomas Gleixner
|
399f8dd9a8 |
signal: Prevent sigqueue caching after task got released
syzbot reported a memory leak related to sigqueue caching.
The assumption that a task cannot cache a sigqueue after the signal handler
has been dropped and exit_task_sigqueue_cache() has been invoked turns out
to be wrong.
Such a task can still invoke release_task(other_task), which cleans up the
signals of 'other_task' and ends up in sigqueue_cache_or_free(), which in
turn will cache the signal because task->sigqueue_cache is NULL. That's
obviously bogus because nothing will free the cached signal of that task
anymore, so the cached item is leaked.
This happens when e.g. the last non-leader thread exits and reaps the
zombie leader.
Prevent this by setting tsk::sigqueue_cache to an error pointer value in
exit_task_sigqueue_cache() which forces any subsequent invocation of
sigqueue_cache_or_free() from that task to hand the sigqueue back to the
kmemcache.
Add comments to all relevant places.
Fixes:
|
||
Peter Zijlstra
|
b03fbd4ff2 |
sched: Introduce task_is_running()
Replace a bunch of 'p->state == TASK_RUNNING' with a new helper: task_is_running(p). Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Davidlohr Bueso <dave@stgolabs.net> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> Acked-by: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20210611082838.222401495@infradead.org |
||
|
Linus Torvalds
|
a0e31f3a38 |
Merge branch 'for-v5.13-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull siginfo fix from Eric Biederman:
"During the merge window an issue with si_perf and the siginfo ABI came
up. The alpha and sparc siginfo structure layout had changed with the
addition of SIGTRAP TRAP_PERF and the new field si_perf.
The reason only alpha and sparc were affected is that they are the
only architectures that use si_trapno.
Looking deeper it was discovered that si_trapno is used for only a few
select signals on alpha and sparc, and that none of the other
_sigfault fields past si_addr are used at all. Which means technically
no regression on alpha and sparc.
While the alignment concerns might be dismissed the abuse of si_errno
by SIGTRAP TRAP_PERF does have the potential to cause regressions in
existing userspace.
While we still have time before userspace starts using and depending
on the new definition siginfo for SIGTRAP TRAP_PERF this set of
changes cleans up siginfo_t.
- The si_trapno field is demoted from magic alpha and sparc status
and made an ordinary union member of the _sigfault member of
siginfo_t. Without moving it of course.
- si_perf is replaced with si_perf_data and si_perf_type ending the
abuse of si_errno.
- Unnecessary additions to signalfd_siginfo are removed"
* 'for-v5.13-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
signalfd: Remove SIL_PERF_EVENT fields from signalfd_siginfo
signal: Deliver all of the siginfo perf data in _perf
signal: Factor force_sig_perf out of perf_sigtrap
signal: Implement SIL_FAULT_TRAPNO
siginfo: Move si_trapno inside the union inside _si_fault
|
||
|
Eric W. Biederman
|
0683b53197 |
signal: Deliver all of the siginfo perf data in _perf
Don't abuse si_errno and deliver all of the perf data in _perf member of siginfo_t. Note: The data field in the perf data structures in a u64 to allow a pointer to be encoded without needed to implement a 32bit and 64bit version of the same structure. There already exists a 32bit and 64bit versions siginfo_t, and the 32bit version can not include a 64bit member as it only has 32bit alignment. So unsigned long is used in siginfo_t instead of a u64 as unsigned long can encode a pointer on all architectures linux supports. v1: https://lkml.kernel.org/r/m11rarqqx2.fsf_-_@fess.ebiederm.org v2: https://lkml.kernel.org/r/20210503203814.25487-10-ebiederm@xmission.com v3: https://lkml.kernel.org/r/20210505141101.11519-11-ebiederm@xmission.com Link: https://lkml.kernel.org/r/20210517195748.8880-4-ebiederm@xmission.com Reviewed-by: Marco Elver <elver@google.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> |
||
|
Eric W. Biederman
|
af5eeab7e8 |
signal: Factor force_sig_perf out of perf_sigtrap
Separate filling in siginfo for TRAP_PERF from deciding that siginal needs to be sent. There are enough little details that need to be correct when properly filling in siginfo_t that it is easy to make mistakes if filling in the siginfo_t is in the same function with other logic. So factor out force_sig_perf to reduce the cognative load of on reviewers, maintainers and implementors. v1: https://lkml.kernel.org/r/m17dkjqqxz.fsf_-_@fess.ebiederm.org v2: https://lkml.kernel.org/r/20210505141101.11519-10-ebiederm@xmission.com Link: https://lkml.kernel.org/r/20210517195748.8880-3-ebiederm@xmission.com Reviewed-by: Marco Elver <elver@google.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> |
||
|
Eric W. Biederman
|
9abcabe311 |
signal: Implement SIL_FAULT_TRAPNO
Now that si_trapno is part of the union in _si_fault and available on all architectures, add SIL_FAULT_TRAPNO and update siginfo_layout to return SIL_FAULT_TRAPNO when the code assumes si_trapno is valid. There is room for future changes to reduce when si_trapno is valid but this is all that is needed to make si_trapno and the other members of the the union in _sigfault mutually exclusive. Update the code that uses siginfo_layout to deal with SIL_FAULT_TRAPNO and have the same code ignore si_trapno in in all other cases. v1: https://lkml.kernel.org/r/m1o8dvs7s7.fsf_-_@fess.ebiederm.org v2: https://lkml.kernel.org/r/20210505141101.11519-6-ebiederm@xmission.com Link: https://lkml.kernel.org/r/20210517195748.8880-2-ebiederm@xmission.com Reviewed-by: Marco Elver <elver@google.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> |
||
|
Eric W. Biederman
|
add0b32ef9 |
siginfo: Move si_trapno inside the union inside _si_fault
It turns out that linux uses si_trapno very sparingly, and as such it can be considered extra information for a very narrow selection of signals, rather than information that is present with every fault reported in siginfo. As such move si_trapno inside the union inside of _si_fault. This results in no change in placement, and makes it eaiser to extend _si_fault in the future as this reduces the number of special cases. In particular with si_trapno included in the union it is no longer a concern that the union must be pointer aligned on most architectures because the union follows immediately after si_addr which is a pointer. This change results in a difference in siginfo field placement on sparc and alpha for the fields si_addr_lsb, si_lower, si_upper, si_pkey, and si_perf. These architectures do not implement the signals that would use si_addr_lsb, si_lower, si_upper, si_pkey, and si_perf. Further these architecture have not yet implemented the userspace that would use si_perf. The point of this change is in fact to correct these placement issues before sparc or alpha grow userspace that cares. This change was discussed[1] and the agreement is that this change is currently safe. [1]: https://lkml.kernel.org/r/CAK8P3a0+uKYwL1NhY6Hvtieghba2hKYGD6hcKx5n8=4Gtt+pHA@mail.gmail.com Acked-by: Marco Elver <elver@google.com> v1: https://lkml.kernel.org/r/m1tunns7yf.fsf_-_@fess.ebiederm.org v2: https://lkml.kernel.org/r/20210505141101.11519-5-ebiederm@xmission.com Link: https://lkml.kernel.org/r/20210517195748.8880-1-ebiederm@xmission.com Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> |
||
|
Alexey Gladkov
|
d646969055 |
Reimplement RLIMIT_SIGPENDING on top of ucounts
The rlimit counter is tied to uid in the user_namespace. This allows rlimit values to be specified in userns even if they are already globally exceeded by the user. However, the value of the previous user_namespaces cannot be exceeded. Changelog v11: * Revert most of changes to fix performance issues. v10: * Fix memory leak on get_ucounts failure. Signed-off-by: Alexey Gladkov <legion@kernel.org> Link: https://lkml.kernel.org/r/df9d7764dddd50f28616b7840de74ec0f81711a8.1619094428.git.legion@kernel.org Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> |
||
|
Linus Torvalds
|
16b3d0cf5b |
Scheduler updates for this cycle are:
- Clean up SCHED_DEBUG: move the decades old mess of sysctl, procfs and debugfs interfaces
to a unified debugfs interface.
- Signals: Allow caching one sigqueue object per task, to improve performance & latencies.
- Improve newidle_balance() irq-off latencies on systems with a large number of CPU cgroups.
- Improve energy-aware scheduling
- Improve the PELT metrics for certain workloads
- Reintroduce select_idle_smt() to improve load-balancing locality - but without the previous
regressions
- Add 'scheduler latency debugging': warn after long periods of pending need_resched. This
is an opt-in feature that requires the enabling of the LATENCY_WARN scheduler feature,
or the use of the resched_latency_warn_ms=xx boot parameter.
- CPU hotplug fixes for HP-rollback, and for the 'fail' interface. Fix remaining
balance_push() vs. hotplug holes/races
- PSI fixes, plus allow /proc/pressure/ files to be written by CAP_SYS_RESOURCE tasks as well
- Fix/improve various load-balancing corner cases vs. capacity margins
- Fix sched topology on systems with NUMA diameter of 3 or above
- Fix PF_KTHREAD vs to_kthread() race
- Minor rseq optimizations
- Misc cleanups, optimizations, fixes and smaller updates
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
- Clean up SCHED_DEBUG: move the decades old mess of sysctl, procfs and
debugfs interfaces to a unified debugfs interface.
- Signals: Allow caching one sigqueue object per task, to improve
performance & latencies.
- Improve newidle_balance() irq-off latencies on systems with a large
number of CPU cgroups.
- Improve energy-aware scheduling
- Improve the PELT metrics for certain workloads
- Reintroduce select_idle_smt() to improve load-balancing locality -
but without the previous regressions
- Add 'scheduler latency debugging': warn after long periods of pending
need_resched. This is an opt-in feature that requires the enabling of
the LATENCY_WARN scheduler feature, or the use of the
resched_latency_warn_ms=xx boot parameter.
- CPU hotplug fixes for HP-rollback, and for the 'fail' interface. Fix
remaining balance_push() vs. hotplug holes/races
- PSI fixes, plus allow /proc/pressure/ files to be written by
CAP_SYS_RESOURCE tasks as well
- Fix/improve various load-balancing corner cases vs. capacity margins
- Fix sched topology on systems with NUMA diameter of 3 or above
- Fix PF_KTHREAD vs to_kthread() race
- Minor rseq optimizations
- Misc cleanups, optimizations, fixes and smaller updates
* tag 'sched-core-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (61 commits)
cpumask/hotplug: Fix cpu_dying() state tracking
kthread: Fix PF_KTHREAD vs to_kthread() race
sched/debug: Fix cgroup_path[] serialization
sched,psi: Handle potential task count underflow bugs more gracefully
sched: Warn on long periods of pending need_resched
sched/fair: Move update_nohz_stats() to the CONFIG_NO_HZ_COMMON block to simplify the code & fix an unused function warning
sched/debug: Rename the sched_debug parameter to sched_verbose
sched,fair: Alternative sched_slice()
sched: Move /proc/sched_debug to debugfs
sched,debug: Convert sysctl sched_domains to debugfs
debugfs: Implement debugfs_create_str()
sched,preempt: Move preempt_dynamic to debug.c
sched: Move SCHED_DEBUG sysctl to debugfs
sched: Don't make LATENCYTOP select SCHED_DEBUG
sched: Remove sched_schedstats sysctl out from under SCHED_DEBUG
sched/numa: Allow runtime enabling/disabling of NUMA balance without SCHED_DEBUG
sched: Use cpu_dying() to fix balance_push vs hotplug-rollback
cpumask: Introduce DYING mask
cpumask: Make cpu_{online,possible,present,active}() inline
rseq: Optimise rseq_get_rseq_cs() and clear_rseq_cs()
...
|
||
|
Linus Torvalds
|
42dec9a936 |
Perf events changes in this cycle were:
- Improve Intel uncore PMU support:
- Parse uncore 'discovery tables' - a new hardware capability enumeration method
introduced on the latest Intel platforms. This table is in a well-defined PCI
namespace location and is read via MMIO. It is organized in an rbtree.
These uncore tables will allow the discovery of standard counter blocks, but
fancier counters still need to be enumerated explicitly.
- Add Alder Lake support
- Improve IIO stacks to PMON mapping support on Skylake servers
- Add Intel Alder Lake PMU support - which requires the introduction of 'hybrid' CPUs
and PMUs. Alder Lake is a mix of Golden Cove ('big') and Gracemont ('small' - Atom derived)
cores.
The CPU-side feature set is entirely symmetrical - but on the PMU side there's
core type dependent PMU functionality.
- Reduce data loss with CPU level hardware tracing on Intel PT / AUX profiling, by
fixing the AUX allocation watermark logic.
- Improve ring buffer allocation on NUMA systems
- Put 'struct perf_event' into their separate kmem_cache pool
- Add support for synchronous signals for select perf events. The immediate motivation
is to support low-overhead sampling-based race detection for user-space code. The
feature consists of the following main changes:
- Add thread-only event inheritance via perf_event_attr::inherit_thread, which limits
inheritance of events to CLONE_THREAD.
- Add the ability for events to not leak through exec(), via perf_event_attr::remove_on_exec.
- Allow the generation of SIGTRAP via perf_event_attr::sigtrap, extend siginfo with an u64
::si_perf, and add the breakpoint information to ::si_addr and ::si_perf if the event is
PERF_TYPE_BREAKPOINT.
The siginfo support is adequate for breakpoints right now - but the new field can be used
to introduce support for other types of metadata passed over siginfo as well.
- Misc fixes, cleanups and smaller updates.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'perf-core-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf event updates from Ingo Molnar:
- Improve Intel uncore PMU support:
- Parse uncore 'discovery tables' - a new hardware capability
enumeration method introduced on the latest Intel platforms. This
table is in a well-defined PCI namespace location and is read via
MMIO. It is organized in an rbtree.
These uncore tables will allow the discovery of standard counter
blocks, but fancier counters still need to be enumerated
explicitly.
- Add Alder Lake support
- Improve IIO stacks to PMON mapping support on Skylake servers
- Add Intel Alder Lake PMU support - which requires the introduction of
'hybrid' CPUs and PMUs. Alder Lake is a mix of Golden Cove ('big')
and Gracemont ('small' - Atom derived) cores.
The CPU-side feature set is entirely symmetrical - but on the PMU
side there's core type dependent PMU functionality.
- Reduce data loss with CPU level hardware tracing on Intel PT / AUX
profiling, by fixing the AUX allocation watermark logic.
- Improve ring buffer allocation on NUMA systems
- Put 'struct perf_event' into their separate kmem_cache pool
- Add support for synchronous signals for select perf events. The
immediate motivation is to support low-overhead sampling-based race
detection for user-space code. The feature consists of the following
main changes:
- Add thread-only event inheritance via
perf_event_attr::inherit_thread, which limits inheritance of
events to CLONE_THREAD.
- Add the ability for events to not leak through exec(), via
perf_event_attr::remove_on_exec.
- Allow the generation of SIGTRAP via perf_event_attr::sigtrap,
extend siginfo with an u64 ::si_perf, and add the breakpoint
information to ::si_addr and ::si_perf if the event is
PERF_TYPE_BREAKPOINT.
The siginfo support is adequate for breakpoints right now - but the
new field can be used to introduce support for other types of
metadata passed over siginfo as well.
- Misc fixes, cleanups and smaller updates.
* tag 'perf-core-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (53 commits)
signal, perf: Add missing TRAP_PERF case in siginfo_layout()
signal, perf: Fix siginfo_t by avoiding u64 on 32-bit architectures
perf/x86: Allow for 8<num_fixed_counters<16
perf/x86/rapl: Add support for Intel Alder Lake
perf/x86/cstate: Add Alder Lake CPU support
perf/x86/msr: Add Alder Lake CPU support
perf/x86/intel/uncore: Add Alder Lake support
perf: Extend PERF_TYPE_HARDWARE and PERF_TYPE_HW_CACHE
perf/x86/intel: Add Alder Lake Hybrid support
perf/x86: Support filter_match callback
perf/x86/intel: Add attr_update for Hybrid PMUs
perf/x86: Add structures for the attributes of Hybrid PMUs
perf/x86: Register hybrid PMUs
perf/x86: Factor out x86_pmu_show_pmu_cap
perf/x86: Remove temporary pmu assignment in event_init
perf/x86/intel: Factor out intel_pmu_check_extra_regs
perf/x86/intel: Factor out intel_pmu_check_event_constraints
perf/x86/intel: Factor out intel_pmu_check_num_counters
perf/x86: Hybrid PMU support for extra_regs
perf/x86: Hybrid PMU support for event constraints
...
|
||
|
Linus Torvalds
|
eb6bbacc46 |
Livepatching changes for 5.13
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Marco Elver
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ed8e50800b |
signal, perf: Add missing TRAP_PERF case in siginfo_layout()
Add the missing TRAP_PERF case in siginfo_layout() for interpreting the
layout correctly as SIL_PERF_EVENT instead of just SIL_FAULT. This
ensures the si_perf field is copied and not just the si_addr field.
This was caught and tested by running the perf_events/sigtrap_threads
kselftest as a 32-bit binary with a 64-bit kernel.
Fixes:
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Ingo Molnar
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d0d252b8ca |
Linux 5.12-rc8
-----BEGIN PGP SIGNATURE----- iQFSBAABCAA8FiEEq68RxlopcLEwq+PEeb4+QwBBGIYFAmB8qHweHHRvcnZhbGRz QGxpbnV4LWZvdW5kYXRpb24ub3JnAAoJEHm+PkMAQRiGEXIIAILUbsTJsNsvZIkZ uQ6SY6gnsPFkRiSRjY0YsZLUnqjTuiiHeTz4gzkonddwdnAp/9g6OIHIEBaeTqBh sTUMU/61Fgtrt/IvkA1yJ3rlawqgwdMe2VdimB+EFhufcSKq+5vpd3MVP4IuGx4E J3psoTU4gVltFs5t+1QjvI3XmByN0Qm8FMRXR7iL+zov1QTmGwR3G6Rn4AymG+QT pdruKboyZPfsrFGSVx7wd3HpFyQcrclEX9rKmBNZqets9d9JGWnqnEN4vQKmwO86 4MV29ucdMXH0AMB3kzGdVp0Ji2Ykt5W0K+MUWbFLtcSxnpu1OyBKGsEAMlRbD7ik gm0bMSw= =qHI0 -----END PGP SIGNATURE----- Merge tag 'v5.12-rc8' into sched/core, to pick up fixes Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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Marco Elver
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fb6cc127e0 |
signal: Introduce TRAP_PERF si_code and si_perf to siginfo
Introduces the TRAP_PERF si_code, and associated siginfo_t field si_perf. These will be used by the perf event subsystem to send signals (if requested) to the task where an event occurred. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> # m68k Acked-by: Arnd Bergmann <arnd@arndb.de> # asm-generic Link: https://lkml.kernel.org/r/20210408103605.1676875-6-elver@google.com |
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Thomas Gleixner
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4bad58ebc8 |
signal: Allow tasks to cache one sigqueue struct
The idea for this originates from the real time tree to make signal delivery for realtime applications more efficient. In quite some of these application scenarios a control tasks signals workers to start their computations. There is usually only one signal per worker on flight. This works nicely as long as the kmem cache allocations do not hit the slow path and cause latencies. To cure this an optimistic caching was introduced (limited to RT tasks) which allows a task to cache a single sigqueue in a pointer in task_struct instead of handing it back to the kmem cache after consuming a signal. When the next signal is sent to the task then the cached sigqueue is used instead of allocating a new one. This solved the problem for this set of application scenarios nicely. The task cache is not preallocated so the first signal sent to a task goes always to the cache allocator. The cached sigqueue stays around until the task exits and is freed when task::sighand is dropped. After posting this solution for mainline the discussion came up whether this would be useful in general and should not be limited to realtime tasks: https://lore.kernel.org/r/m11rcu7nbr.fsf@fess.ebiederm.org One concern leading to the original limitation was to avoid a large amount of pointlessly cached sigqueues in alive tasks. The other concern was vs. RLIMIT_SIGPENDING as these cached sigqueues are not accounted for. The accounting problem is real, but on the other hand slightly academic. After gathering some statistics it turned out that after boot of a regular distro install there are less than 10 sigqueues cached in ~1500 tasks. In case of a 'mass fork and fire signal to child' scenario the extra 80 bytes of memory per task are well in the noise of the overall memory consumption of the fork bomb. If this should be limited then this would need an extra counter in struct user, more atomic instructions and a seperate rlimit. Yet another tunable which is mostly unused. The caching is actually used. After boot and a full kernel compile on a 64CPU machine with make -j128 the number of 'allocations' looks like this: From slab: 23996 From task cache: 52223 I.e. it reduces the number of slab cache operations by ~68%. A typical pattern there is: <...>-58490 __sigqueue_alloc: for 58488 from slab ffff8881132df460 <...>-58488 __sigqueue_free: cache ffff8881132df460 <...>-58488 __sigqueue_alloc: for 1149 from cache ffff8881103dc550 bash-1149 exit_task_sighand: free ffff8881132df460 bash-1149 __sigqueue_free: cache ffff8881103dc550 The interesting sequence is that the exiting task 58488 grabs the sigqueue from bash's task cache to signal exit and bash sticks it back into it's own cache. Lather, rinse and repeat. The caching is probably not noticable for the general use case, but the benefit for latency sensitive applications is clear. While kmem caches are usually just serving from the fast path the slab merging (default) can depending on the usage pattern of the merged slabs cause occasional slow path allocations. The time spared per cached entry is a few micro seconds per signal which is not relevant for e.g. a kernel build, but for signal heavy workloads it's measurable. As there is no real downside of this caching mechanism making it unconditionally available is preferred over more conditional code or new magic tunables. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Link: https://lkml.kernel.org/r/87sg4lbmxo.fsf@nanos.tec.linutronix.de |
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Thomas Gleixner
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69995ebbb9 |
signal: Hand SIGQUEUE_PREALLOC flag to __sigqueue_alloc()
There is no point in having the conditional at the callsite. Just hand in the allocation mode flag to __sigqueue_alloc() and use it to initialize sigqueue::flags. No functional change. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210322092258.898677147@linutronix.de |
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Miroslav Benes
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8df1947c71 |
livepatch: Replace the fake signal sending with TIF_NOTIFY_SIGNAL infrastructure
Livepatch sends a fake signal to all remaining blocking tasks of a
running transition after a set period of time. It uses TIF_SIGPENDING
flag for the purpose. Commit
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Jens Axboe
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1e4cf0d3d0 |
Revert "signal: don't allow STOP on PF_IO_WORKER threads"
This reverts commit
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Jens Axboe
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e8b33b8cfa |
Revert "kernel: treat PF_IO_WORKER like PF_KTHREAD for ptrace/signals"
This reverts commit
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Jens Axboe
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5a842a7448 |
Revert "signal: don't allow sending any signals to PF_IO_WORKER threads"
This reverts commit
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Jens Axboe
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10442994ba |
kernel: don't call do_exit() for PF_IO_WORKER threads
Right now we're never calling get_signal() from PF_IO_WORKER threads, but in preparation for doing so, don't handle a fatal signal for them. The workers have state they need to cleanup when exiting, so just return instead of calling do_exit() on their behalf. The threads themselves will detect a fatal signal and do proper shutdown. Signed-off-by: Jens Axboe <axboe@kernel.dk> |