| Message ID | 1456928778-22491-4-git-send-email-mark.rutland@arm.com |
|---|---|
| State | Accepted |
| Commit | 0d97e6d8024c71cc838b292c01d5bd951e080eba |
| Headers | show |
On Wed, Mar 02, 2016 at 02:26:18PM +0000, Mark Rutland wrote: > Functions which the compiler has instrumented for ASAN place poison on > the stack shadow upon entry and remove this poison prior to returning. > > In the case of cpuidle, CPUs exit the kernel a number of levels deep > in C code. Any instrumented functions on this critical path will leave > portions of the stack shadow poisoned. > > If CPUs lose context and return to the kernel via a cold path, we > restore a prior context saved in __cpu_suspend_enter are forgotten, and > we never remove the poison they placed in the stack shadow area by > functions calls between this and the actual exit of the kernel. > > Thus, (depending on stackframe layout) subsequent calls to instrumented > functions may hit this stale poison, resulting in (spurious) KASAN > splats to the console. > > To avoid this, clear any stale poison from the idle thread for a CPU > prior to bringing a CPU online. > > Signed-off-by: Mark Rutland <mark.rutland@arm.com> > Cc: Alexander Potapenko <glider@google.com> > Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > --- > arch/arm64/kernel/sleep.S | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S > index e33fe33..fd10eb6 100644 > --- a/arch/arm64/kernel/sleep.S > +++ b/arch/arm64/kernel/sleep.S > @@ -145,6 +145,10 @@ ENTRY(cpu_resume_mmu) > ENDPROC(cpu_resume_mmu) > .popsection > cpu_resume_after_mmu: > +#ifdef CONFIG_KASAN > + mov x0, sp > + bl kasan_unpoison_remaining_stack > +#endif Lorenzo, as this was following your suggestion [1], I hope that this patch looks ok to you? Are you happy to provide an Ack / Reviewed-by? Thanks, Mark. [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2016-March/413061.html
diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S index e33fe33..fd10eb6 100644 --- a/arch/arm64/kernel/sleep.S +++ b/arch/arm64/kernel/sleep.S @@ -145,6 +145,10 @@ ENTRY(cpu_resume_mmu) ENDPROC(cpu_resume_mmu) .popsection cpu_resume_after_mmu: +#ifdef CONFIG_KASAN + mov x0, sp + bl kasan_unpoison_remaining_stack +#endif mov x0, #0 // return zero on success ldp x19, x20, [sp, #16] ldp x21, x22, [sp, #32]
Functions which the compiler has instrumented for ASAN place poison on the stack shadow upon entry and remove this poison prior to returning. In the case of cpuidle, CPUs exit the kernel a number of levels deep in C code. Any instrumented functions on this critical path will leave portions of the stack shadow poisoned. If CPUs lose context and return to the kernel via a cold path, we restore a prior context saved in __cpu_suspend_enter are forgotten, and we never remove the poison they placed in the stack shadow area by functions calls between this and the actual exit of the kernel. Thus, (depending on stackframe layout) subsequent calls to instrumented functions may hit this stale poison, resulting in (spurious) KASAN splats to the console. To avoid this, clear any stale poison from the idle thread for a CPU prior to bringing a CPU online. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Alexander Potapenko <glider@google.com> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Cc: Will Deacon <will.deacon@arm.com> --- arch/arm64/kernel/sleep.S | 4 ++++ 1 file changed, 4 insertions(+) -- 1.9.1