Messages in this thread | | | From | Andy Lutomirski <> | Date | Tue, 12 Jul 2016 11:03:02 -0700 | Subject | Re: [kernel-hardening] [PATCH v5 13/32] x86/mm/64: In vmalloc_fault(), use CR3 instead of current->active_mm |
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On Tue, Jul 12, 2016 at 10:51 AM, Dave Hansen <dave.hansen@intel.com> wrote: > On 07/11/2016 01:53 PM, Andy Lutomirski wrote: >> If we get a vmalloc fault while current->active_mm->pgd doesn't >> match CR3, we'll crash without this change. I've seen this failure >> mode on heavily instrumented kernels with virtually mapped stacks. > > When does this happen, btw? Crossing page boundaries on the stack > between the time we swap mm's and the time we switch stacks?
This can happen for any vmalloc fault between the mm swap and writing to current or current->active_mm. I hit it when playing with KASAN during the first clone. (KASAN has other issues, but this was one of them AFAICT.)
--Andy
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