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x86/mm/64: In vmalloc_fault(), use CR3 instead of current->active_mm 

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.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/4650d7674185f165ed8fdf9ac4c5c35c5c179ba8.1468527351.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2016-07-14 13:22:54 -07:00 committed by Ingo Molnar
parent 98f30b1207
commit 46aea38734
1 changed files with 1 additions and 1 deletions
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2
arch/x86/mm/fault.c
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@ -439,7 +439,7 @@ static noinline int vmalloc_fault(unsigned long address)
* happen within a race in page table update. In the later
* case just flush:
*/
pgd = pgd_offset(current->active_mm, address);
pgd = (pgd_t *)__va(read_cr3()) + pgd_index(address);
pgd_ref = pgd_offset_k(address);
if (pgd_none(*pgd_ref))
return -1;