On Tue, Jul 12, 2016 at 10:51 AM, Dave Hansen <[email protected]> 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
