diff options
| author | Nathan Chancellor <nathan@kernel.org> | 2023-06-07 14:20:59 -0700 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2023-06-08 10:28:39 +0200 |
| commit | 093d9b240a1fa261ff8aeb7c7cc484dedacfda53 (patch) | |
| tree | b9f3cf77ae49496a5475e6f46f30d8d5fed1fd35 | |
| parent | ef558b4b7bbbf7e115c87e4da21ce86444d6ec3b (diff) | |
percpu: Fix self-assignment of __old in raw_cpu_generic_try_cmpxchg()
After commit c5c0ba953b8c ("percpu: Add {raw,this}_cpu_try_cmpxchg()"),
clang built ARCH=arm and ARCH=arm64 kernels with CONFIG_INIT_STACK_NONE
started panicking on boot in alloc_vmap_area():
[ 0.000000] kernel BUG at mm/vmalloc.c:1638!
[ 0.000000] Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
[ 0.000000] Modules linked in:
[ 0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.4.0-rc2-ARCH+ #1
[ 0.000000] Hardware name: linux,dummy-virt (DT)
[ 0.000000] pstate: 200000c9 (nzCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 0.000000] pc : alloc_vmap_area+0x7ec/0x7f8
[ 0.000000] lr : alloc_vmap_area+0x7e8/0x7f8
Compiling mm/vmalloc.c with W=2 reveals an instance of -Wshadow, which
helps uncover that through macro expansion, '__old = *(ovalp)' in
raw_cpu_generic_try_cmpxchg() can become '__old = *(&__old)' through
raw_cpu_generic_cmpxchg(), which results in garbage being assigned to
the inner __old and the cmpxchg not working properly.
Add an extra underscore to __old in raw_cpu_generic_try_cmpxchg() so
that there is no more self-assignment, which resolves the panics.
Closes: https://github.com/ClangBuiltLinux/linux/issues/1868
Fixes: c5c0ba953b8c ("percpu: Add {raw,this}_cpu_try_cmpxchg()")
Debugged-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230607-fix-shadowing-in-raw_cpu_generic_try_cmpxchg-v1-1-8f0a3d930d43@kernel.org
| -rw-r--r-- | include/asm-generic/percpu.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h index 68c410e85cd7..94cbd50cc870 100644 --- a/include/asm-generic/percpu.h +++ b/include/asm-generic/percpu.h @@ -101,9 +101,9 @@ do { \ #define raw_cpu_generic_try_cmpxchg(pcp, ovalp, nval) \ ({ \ typeof(pcp) *__p = raw_cpu_ptr(&(pcp)); \ - typeof(pcp) __val = *__p, __old = *(ovalp); \ + typeof(pcp) __val = *__p, ___old = *(ovalp); \ bool __ret; \ - if (__val == __old) { \ + if (__val == ___old) { \ *__p = nval; \ __ret = true; \ } else { \ |