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uevent_show() wants to de-reference dev->driver->name. There is no clean
way for a device attribute to de-reference dev->driver unless that
attribute is defined via (struct device_driver).dev_groups. Instead, the
anti-pattern of taking the device_lock() in the attribute handler risks
deadlocks with code paths that remove device attributes while holding
the lock.
This deadlock is typically invisible to lockdep given the device_lock()
is marked lockdep_set_novalidate_class(), but some subsystems allocate a
local lockdep key for @dev->mutex to reveal reports of the form:
======================================================
WARNING: possible circular locking dependency detected
6.10.0-rc7+ #275 Tainted: G OE N
------------------------------------------------------
modprobe/2374 is trying to acquire lock:
ffff8c2270070de0 (kn->active#6){++++}-{0:0}, at: __kernfs_remove+0xde/0x220
but task is already holding lock:
ffff8c22016e88f8 (&cxl_root_key){+.+.}-{3:3}, at: device_release_driver_internal+0x39/0x210
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&cxl_root_key){+.+.}-{3:3}:
__mutex_lock+0x99/0xc30
uevent_show+0xac/0x130
dev_attr_show+0x18/0x40
sysfs_kf_seq_show+0xac/0xf0
seq_read_iter+0x110/0x450
vfs_read+0x25b/0x340
ksys_read+0x67/0xf0
do_syscall_64+0x75/0x190
entry_SYSCALL_64_after_hwframe+0x76/0x7e
-> #0 (kn->active#6){++++}-{0:0}:
__lock_acquire+0x121a/0x1fa0
lock_acquire+0xd6/0x2e0
kernfs_drain+0x1e9/0x200
__kernfs_remove+0xde/0x220
kernfs_remove_by_name_ns+0x5e/0xa0
device_del+0x168/0x410
device_unregister+0x13/0x60
devres_release_all+0xb8/0x110
device_unbind_cleanup+0xe/0x70
device_release_driver_internal+0x1c7/0x210
driver_detach+0x47/0x90
bus_remove_driver+0x6c/0xf0
cxl_acpi_exit+0xc/0x11 [cxl_acpi]
__do_sys_delete_module.isra.0+0x181/0x260
do_syscall_64+0x75/0x190
entry_SYSCALL_64_after_hwframe+0x76/0x7e
The observation though is that driver objects are typically much longer
lived than device objects. It is reasonable to perform lockless
de-reference of a @driver pointer even if it is racing detach from a
device. Given the infrequency of driver unregistration, use
synchronize_rcu() in module_remove_driver() to close any potential
races. It is potentially overkill to suffer synchronize_rcu() just to
handle the rare module removal racing uevent_show() event.
Thanks to Tetsuo Handa for the debug analysis of the syzbot report [1].
Fixes: c0a40097f0bc ("drivers: core: synchronize really_probe() and dev_uevent()")
Reported-by: syzbot+4762dd74e32532cda5ff@syzkaller.appspotmail.com
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Closes: http://lore.kernel.org/5aa5558f-90a4-4864-b1b1-5d6784c5607d@I-love.SAKURA.ne.jp [1]
Link: http://lore.kernel.org/669073b8ea479_5fffa294c1@dwillia2-xfh.jf.intel.com.notmuch
Cc: stable@vger.kernel.org
Cc: Ashish Sangwan <a.sangwan@samsung.com>
Cc: Namjae Jeon <namjae.jeon@samsung.com>
Cc: Dirk Behme <dirk.behme@de.bosch.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/172081332794.577428.9738802016494057132.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The functions module_add_driver() and module_remove_driver() do not
modify the struct device_driver structure directly, so they are safe to
be marked as a constant pointer type.
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Link: https://lore.kernel.org/r/2024070850-entering-grandson-205e@gregkh
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The sysfs_create_link() return code is marked as __must_check, but the
module_add_driver() function tries hard to not care, by assigning the
return code to a variable. When building with 'make W=1', gcc still
warns because this variable is only assigned but not used:
drivers/base/module.c: In function 'module_add_driver':
drivers/base/module.c:36:6: warning: variable 'no_warn' set but not used [-Wunused-but-set-variable]
Rework the code to properly unwind and return the error code to the
caller. My reading of the original code was that it tries to
not fail when the links already exist, so keep ignoring -EEXIST
errors.
Fixes: e17e0f51aeea ("Driver core: show drivers in /sys/module/")
See-also: 4a7fb6363f2d ("add __must_check to device management code")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/20240408080616.3911573-1-arnd@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Now that the SPDX tag is in all driver core files, that identifies the
license in a specific and legally-defined manner. So the extra GPL text
wording can be removed as it is no longer needed at all.
This is done on a quest to remove the 700+ different ways that files in
the kernel describe the GPL license text. And there's unneeded stuff
like the address (sometimes incorrect) for the FSF which is never
needed.
No copyright headers or other non-license-description text was removed.
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: "Luis R. Rodriguez" <mcgrof@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
It's good to have SPDX identifiers in all files to make it easier to
audit the kernel tree for correct licenses.
Update the driver core files files with the correct SPDX license
identifier based on the license text in the file itself. The SPDX
identifier is a legally binding shorthand, which can be used instead of
the full boiler plate text.
This work is based on a script and data from Thomas Gleixner, Philippe
Ombredanne, and Kate Stewart.
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: "Luis R. Rodriguez" <mcgrof@kernel.org>
Cc: William Breathitt Gray <vilhelm.gray@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Modules which register drivers via standard path (driver_register) in
parallel can cause a warning:
WARNING: CPU: 2 PID: 3492 at ../fs/sysfs/dir.c:31 sysfs_warn_dup+0x62/0x80
sysfs: cannot create duplicate filename '/module/saa7146/drivers'
Modules linked in: hexium_gemini(+) mxb(+) ...
...
Call Trace:
...
[<ffffffff812e63a2>] sysfs_warn_dup+0x62/0x80
[<ffffffff812e6487>] sysfs_create_dir_ns+0x77/0x90
[<ffffffff8140f2c4>] kobject_add_internal+0xb4/0x340
[<ffffffff8140f5b8>] kobject_add+0x68/0xb0
[<ffffffff8140f631>] kobject_create_and_add+0x31/0x70
[<ffffffff8157a703>] module_add_driver+0xc3/0xd0
[<ffffffff8155e5d4>] bus_add_driver+0x154/0x280
[<ffffffff815604c0>] driver_register+0x60/0xe0
[<ffffffff8145bed0>] __pci_register_driver+0x60/0x70
[<ffffffffa0273e14>] saa7146_register_extension+0x64/0x90 [saa7146]
[<ffffffffa0033011>] hexium_init_module+0x11/0x1000 [hexium_gemini]
...
As can be (mostly) seen, driver_register causes this call sequence:
-> bus_add_driver
-> module_add_driver
-> module_create_drivers_dir
The last one creates "drivers" directory in /sys/module/<...>. When
this is done in parallel, the directory is attempted to be created
twice at the same time.
This can be easily reproduced by loading mxb and hexium_gemini in
parallel:
while :; do
modprobe mxb &
modprobe hexium_gemini
wait
rmmod mxb hexium_gemini saa7146_vv saa7146
done
saa7146 calls pci_register_driver for both mxb and hexium_gemini,
which means /sys/module/saa7146/drivers is to be created for both of
them.
Fix this by a new mutex in module_create_drivers_dir which makes the
test-and-create "drivers" dir atomic.
I inverted the condition and removed 'return' to avoid multiple
unlocks or a goto.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Fixes: fe480a2675ed (Modules: only add drivers/ direcory if needed)
Cc: v2.6.21+ <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kasprintf combines kmalloc and sprintf, and takes care of the size
calculation itself.
The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)
// <smpl>
@@
expression a,flag;
expression list args;
statement S;
@@
a =
- \(kmalloc\|kzalloc\)(...,flag)
+ kasprintf(flag,args)
<... when != a
if (a == NULL || ...) S
...>
- sprintf(a,args);
// </smpl>
Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files. percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.
percpu.h -> slab.h dependency is about to be removed. Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability. As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.
http://userweb.kernel.org/~tj/misc/slabh-sweep.py
The script does the followings.
* Scan files for gfp and slab usages and update includes such that
only the necessary includes are there. ie. if only gfp is used,
gfp.h, if slab is used, slab.h.
* When the script inserts a new include, it looks at the include
blocks and try to put the new include such that its order conforms
to its surrounding. It's put in the include block which contains
core kernel includes, in the same order that the rest are ordered -
alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
doesn't seem to be any matching order.
* If the script can't find a place to put a new include (mostly
because the file doesn't have fitting include block), it prints out
an error message indicating which .h file needs to be added to the
file.
The conversion was done in the following steps.
1. The initial automatic conversion of all .c files updated slightly
over 4000 files, deleting around 700 includes and adding ~480 gfp.h
and ~3000 slab.h inclusions. The script emitted errors for ~400
files.
2. Each error was manually checked. Some didn't need the inclusion,
some needed manual addition while adding it to implementation .h or
embedding .c file was more appropriate for others. This step added
inclusions to around 150 files.
3. The script was run again and the output was compared to the edits
from #2 to make sure no file was left behind.
4. Several build tests were done and a couple of problems were fixed.
e.g. lib/decompress_*.c used malloc/free() wrappers around slab
APIs requiring slab.h to be added manually.
5. The script was run on all .h files but without automatically
editing them as sprinkling gfp.h and slab.h inclusions around .h
files could easily lead to inclusion dependency hell. Most gfp.h
inclusion directives were ignored as stuff from gfp.h was usually
wildly available and often used in preprocessor macros. Each
slab.h inclusion directive was examined and added manually as
necessary.
6. percpu.h was updated not to include slab.h.
7. Build test were done on the following configurations and failures
were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my
distributed build env didn't work with gcov compiles) and a few
more options had to be turned off depending on archs to make things
build (like ipr on powerpc/64 which failed due to missing writeq).
* x86 and x86_64 UP and SMP allmodconfig and a custom test config.
* powerpc and powerpc64 SMP allmodconfig
* sparc and sparc64 SMP allmodconfig
* ia64 SMP allmodconfig
* s390 SMP allmodconfig
* alpha SMP allmodconfig
* um on x86_64 SMP allmodconfig
8. percpu.h modifications were reverted so that it could be applied as
a separate patch and serve as bisection point.
Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
This patch removes the kobject, and a few other driver-core-only fields
out of struct driver and into the driver core only. Now drivers can be
safely create on the stack or statically (like they currently are.)
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
The module driver specific code should belong in the driver core, not in
the kernel/ directory. So move this code. This is done in preparation
for some struct device_driver rework that should be confined to the
driver core code only.
This also lets us keep from exporting these functions, as no external
code should ever be calling it.
Thanks to Andrew Morton for the !CONFIG_MODULES fix.
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
