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commit 87e0d4f0f37fb0c8c4aeeac46fff5e957738df79 upstream.
Prasad reported that he has seen crashes in BPF subsystem with netd
on Android with arm64 in the form of (note, the taint is unrelated):
[ 4134.721483] Unable to handle kernel paging request at virtual address 800000001
[ 4134.820925] Mem abort info:
[ 4134.901283] Exception class = DABT (current EL), IL = 32 bits
[ 4135.016736] SET = 0, FnV = 0
[ 4135.119820] EA = 0, S1PTW = 0
[ 4135.201431] Data abort info:
[ 4135.301388] ISV = 0, ISS = 0x00000021
[ 4135.359599] CM = 0, WnR = 0
[ 4135.470873] user pgtable: 4k pages, 39-bit VAs, pgd = ffffffe39b946000
[ 4135.499757] [0000000800000001] *pgd=0000000000000000, *pud=0000000000000000
[ 4135.660725] Internal error: Oops: 96000021 [#1] PREEMPT SMP
[ 4135.674610] Modules linked in:
[ 4135.682883] CPU: 5 PID: 1260 Comm: netd Tainted: G S W 4.14.19+ #1
[ 4135.716188] task: ffffffe39f4aa380 task.stack: ffffff801d4e0000
[ 4135.731599] PC is at bpf_prog_add+0x20/0x68
[ 4135.741746] LR is at bpf_prog_inc+0x20/0x2c
[ 4135.751788] pc : [<ffffff94ab7ad584>] lr : [<ffffff94ab7ad638>] pstate: 60400145
[ 4135.769062] sp : ffffff801d4e3ce0
[...]
[ 4136.258315] Process netd (pid: 1260, stack limit = 0xffffff801d4e0000)
[ 4136.273746] Call trace:
[...]
[ 4136.442494] 3ca0: ffffff94ab7ad584 0000000060400145 ffffffe3a01bf8f8 0000000000000006
[ 4136.460936] 3cc0: 0000008000000000 ffffff94ab844204 ffffff801d4e3cf0 ffffff94ab7ad584
[ 4136.479241] [<ffffff94ab7ad584>] bpf_prog_add+0x20/0x68
[ 4136.491767] [<ffffff94ab7ad638>] bpf_prog_inc+0x20/0x2c
[ 4136.504536] [<ffffff94ab7b5d08>] bpf_obj_get_user+0x204/0x22c
[ 4136.518746] [<ffffff94ab7ade68>] SyS_bpf+0x5a8/0x1a88
Android's netd was basically pinning the uid cookie BPF map in BPF
fs (/sys/fs/bpf/traffic_cookie_uid_map) and later on retrieving it
again resulting in above panic. Issue is that the map was wrongly
identified as a prog! Above kernel was compiled with clang 4.0,
and it turns out that clang decided to merge the bpf_prog_iops and
bpf_map_iops into a single memory location, such that the two i_ops
could then not be distinguished anymore.
Reason for this miscompilation is that clang has the more aggressive
-fmerge-all-constants enabled by default. In fact, clang source code
has a comment about it in lib/AST/ExprConstant.cpp on why it is okay
to do so:
Pointers with different bases cannot represent the same object.
(Note that clang defaults to -fmerge-all-constants, which can
lead to inconsistent results for comparisons involving the address
of a constant; this generally doesn't matter in practice.)
The issue never appeared with gcc however, since gcc does not enable
-fmerge-all-constants by default and even *explicitly* states in
it's option description that using this flag results in non-conforming
behavior, quote from man gcc:
Languages like C or C++ require each variable, including multiple
instances of the same variable in recursive calls, to have distinct
locations, so using this option results in non-conforming behavior.
There are also various clang bug reports open on that matter [1],
where clang developers acknowledge the non-conforming behavior,
and refer to disabling it with -fno-merge-all-constants. But even
if this gets fixed in clang today, there are already users out there
that triggered this. Thus, fix this issue by explicitly adding
-fno-merge-all-constants to the kernel's Makefile to generically
disable this optimization, since potentially other places in the
kernel could subtly break as well.
Note, there is also a flag called -fmerge-constants (not supported
by clang), which is more conservative and only applies to strings
and it's enabled in gcc's -O/-O2/-O3/-Os optimization levels. In
gcc's code, the two flags -fmerge-{all-,}constants share the same
variable internally, so when disabling it via -fno-merge-all-constants,
then we really don't merge any const data (e.g. strings), and text
size increases with gcc (14,927,214 -> 14,942,646 for vmlinux.o).
$ gcc -fverbose-asm -O2 foo.c -S -o foo.S
-> foo.S lists -fmerge-constants under options enabled
$ gcc -fverbose-asm -O2 -fno-merge-all-constants foo.c -S -o foo.S
-> foo.S doesn't list -fmerge-constants under options enabled
$ gcc -fverbose-asm -O2 -fno-merge-all-constants -fmerge-constants foo.c -S -o foo.S
-> foo.S lists -fmerge-constants under options enabled
Thus, as a workaround we need to set both -fno-merge-all-constants
*and* -fmerge-constants in the Makefile in order for text size to
stay as is.
[1] https://bugs.llvm.org/show_bug.cgi?id=18538
Reported-by: Prasad Sodagudi <psodagud@codeaurora.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Chenbo Feng <fengc@google.com>
Cc: Richard Smith <richard-llvm@metafoo.co.uk>
Cc: Chandler Carruth <chandlerc@gmail.com>
Cc: linux-kernel@vger.kernel.org
Tested-by: Prasad Sodagudi <psodagud@codeaurora.org>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit e572d0887137acfc53f18175522964ec19d88175 upstream.
When doing a kernel build with 'make -s', everything is silenced except
the objtool build. That's because the tools tree support for silent
builds is some combination of missing and broken.
Three changes are needed to fix it:
- Makefile: propagate '-s' to the sub-make's MAKEFLAGS variable so the
tools Makefiles can see it.
- tools/scripts/Makefile.include: fix the tools Makefiles' ability to
recognize '-s'. The MAKE_VERSION and MAKEFLAGS checks are copied from
the top-level Makefile. This silences the "DESCEND objtool" message.
- tools/build/Makefile.build: add support to the tools Build files for
recognizing '-s'. Again the MAKE_VERSION and MAKEFLAGS checks are
copied from the top-level Makefile. This silences all the object
compile/link messages.
Reported-and-Tested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Michal Marek <mmarek@suse.com>
Link: http://lkml.kernel.org/r/e8967562ef640c3ae9a76da4ae0f4e47df737c34.1484799200.git.jpoimboe@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 3ce120b16cc548472f80cf8644f90eda958cf1b6 upstream.
It appears that hardened gentoo enables "-fstack-check" by default for
gcc.
That doesn't work _at_all_ for the kernel, because the kernel stack
doesn't act like a user stack at all: it's much smaller, and it doesn't
auto-expand on use. So the extra "probe one page below the stack" code
generated by -fstack-check just breaks the kernel in horrible ways,
causing infinite double faults etc.
[ I have to say, that the particular code gcc generates looks very
stupid even for user space where it works, but that's a separate
issue. ]
Reported-and-tested-by: Alexander Tsoy <alexander@tsoy.me>
Reported-and-tested-by: Toralf Förster <toralf.foerster@gmx.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 433dc2ebe7d17dd21cba7ad5c362d37323592236 ]
Some $(call cc-option,...) are invoked very early, even before
KBUILD_CFLAGS, etc. are initialized.
The returned string from $(call cc-option,...) depends on
KBUILD_CPPFLAGS, KBUILD_CFLAGS, and GCC_PLUGINS_CFLAGS.
Since they are exported, they are not empty when the top Makefile
is recursively invoked.
The recursion occurs in several places. For example, the top
Makefile invokes itself for silentoldconfig. "make tinyconfig",
"make rpm-pkg" are the cases, too.
In those cases, the second call of cc-option from the same line
runs a different shell command due to non-pristine KBUILD_CFLAGS.
To get the same result all the time, KBUILD_* and GCC_PLUGINS_CFLAGS
must be initialized before any call of cc-option. This avoids
garbage data in the .cache.mk file.
Move all calls of cc-option below the config targets because target
compiler flags are unnecessary for Kconfig.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
