Messages in this thread Patch in this message | | | Date | Fri, 19 Feb 2016 10:52:29 +0000 | From | Lorenzo Pieralisi <> | Subject | Re: [PATCH] arm64: kasan: clear stale stack poison |
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On Thu, Feb 18, 2016 at 06:13:57PM +0000, Catalin Marinas wrote: > On Thu, Feb 18, 2016 at 06:03:54PM +0000, Will Deacon wrote: > > On Thu, Feb 18, 2016 at 05:54:47PM +0000, Catalin Marinas wrote: > > > On Thu, Feb 18, 2016 at 05:27:38PM +0000, Mark Rutland wrote: > > > > @@ -145,6 +146,7 @@ ENTRY(cpu_resume_mmu) > > > > ENDPROC(cpu_resume_mmu) > > > > .popsection > > > > cpu_resume_after_mmu: > > > > + kasan_unpoison_stack 96 > > > > > > I don't think the 96 here is needed since we populate the stack in > > > assembly (__cpu_suspend_enter) and unwind it again still in assembly > > > (cpu_resume_after_mmu), so no KASAN shadow writes/reads. > > > > > > Otherwise the patch looks fine. > > > > I'd much rather it was written in C -- is there a reason we can't do > > that if we use a separate compilation unit where the compiler will > > honour the fno-sanitize flag? > > A simple, non-sanitised C wrapper around __cpu_suspend_enter() would > probably work. We need to make sure it is static inline when !KASAN to > avoid an unnecessary function call. Or we just move cpu_suspend() to a > different compilation unit, though that's a slightly larger function > which we may want to track under KASAN.
Both options are ok with me. There is one more. We pass the "saved" sp to __cpu_suspend_save (ie in cpu_suspend_ctx), you can stash it and use it in the resume path (through logical cpu indexing) to carry out the kasan clean-up, in C, with no wrapper needed.
With James' hibernate patches:
http://lists.infradead.org/pipermail/linux-arm-kernel/2016-February/408597.html
this is going to be even easier, since the struct above is on the cpu_suspend stack upon cpu_resume, so you can use the sp in there straight away.
We can put together a fix following Catalin's suggestion and when James' patches land in mainline we will update the code.
Thanks, Lorenzo
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