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| author | Nathan Chancellor <natechancellor@gmail.com> | 2019-04-17 00:21:21 -0700 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2019-04-18 18:17:08 +0100 |
| commit | ff8acf929014b7f87315588e0daf8597c8aa9d1c (patch) | |
| tree | e62ff416b393abf3f39ab1096683508cd8fb661a /arch | |
| parent | dc4060a5dc2557e6b5aa813bf5b73677299d62d2 (diff) | |
| download | lwn-ff8acf929014b7f87315588e0daf8597c8aa9d1c.tar.gz lwn-ff8acf929014b7f87315588e0daf8597c8aa9d1c.zip | |
arm64: futex: Restore oldval initialization to work around buggy compilers
Commit 045afc24124d ("arm64: futex: Fix FUTEX_WAKE_OP atomic ops with
non-zero result value") removed oldval's zero initialization in
arch_futex_atomic_op_inuser because it is not necessary. Unfortunately,
Android's arm64 GCC 4.9.4 [1] does not agree:
../kernel/futex.c: In function 'do_futex':
../kernel/futex.c:1658:17: warning: 'oldval' may be used uninitialized
in this function [-Wmaybe-uninitialized]
return oldval == cmparg;
^
In file included from ../kernel/futex.c:73:0:
../arch/arm64/include/asm/futex.h:53:6: note: 'oldval' was declared here
int oldval, ret, tmp;
^
GCC fails to follow that when ret is non-zero, futex_atomic_op_inuser
returns right away, avoiding the uninitialized use that it claims.
Restoring the zero initialization works around this issue.
[1]: https://android.googlesource.com/platform/prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9/
Cc: stable@vger.kernel.org
Fixes: 045afc24124d ("arm64: futex: Fix FUTEX_WAKE_OP atomic ops with non-zero result value")
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm64/include/asm/futex.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/arm64/include/asm/futex.h b/arch/arm64/include/asm/futex.h index e1d95f08f8e1..c7e1a7837706 100644 --- a/arch/arm64/include/asm/futex.h +++ b/arch/arm64/include/asm/futex.h @@ -50,7 +50,7 @@ do { \ static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *_uaddr) { - int oldval, ret, tmp; + int oldval = 0, ret, tmp; u32 __user *uaddr = __uaccess_mask_ptr(_uaddr); pagefault_disable(); |