Messages in this thread | | | Subject | Re: [PATCH] x86/entry/64: wipe KASAN stack shadow in rewind_stack_do_exit() | From | Andy Lutomirski <> | Date | Tue, 28 Aug 2018 12:57:36 -0700 |
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> On Aug 28, 2018, at 4:33 AM, Andrey Ryabinin <aryabinin@virtuozzo.com> wrote: > > > > On 08/28/2018 01:38 PM, Jann Horn wrote: > >>> >>> >>> Why this has to be done in the rewind_stack_do_exit()? >>> Are there any problems with calling the kasan_unpoison_task_stack(current) from oops_end(), before the rewind_stack_do_exit()? >> >> Ooh, good point! I didn't see that KASAN instrumentation is disabled >> for dumpstack.c. > > It doesn't really matter. This would work with instrumented oops_end() as well. > kasan_unpoison_task_stack() will unpoison everything including oops_end's stack. > It would be also ok if kasan_unpoison_task_stack() instrumented, or calling any number of instrumented functions > in between kasan_unpoison_task_stack() and rewind_stack_do_exit(). As long as we return from these functions before > the rewind_stack_do_exit(), the stack will be unpoisoned on return.
I think that, if all this is in C, we need rewind_stack_do_exit()’s caller to be uninstrumented. Which it is.
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