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authorAndi Kleen <andi@firstfloor.org>2009-01-09 15:17:43 -0500
committerIngo Molnar <mingo@elte.hu>2009-01-12 13:24:21 -0500
commitf313e12308f7c5ea645f18e759d104d088b18615 (patch)
tree4043dfa82448c1ef1bba81e58eb1fe162e82a69c /arch/x86
parentf45ac22ae2b8fc5b4c32d9b8d17ea419a8701d89 (diff)
x86: avoid theoretical vmalloc fault loop
Ajith Kumar noticed: I was going through the vmalloc fault handling for x86_64 and am unclear about the following lines in the vmalloc_fault() function. pgd = pgd_offset(current->mm ?: &init_mm, address); pgd_ref = pgd_offset_k(address); Here the intention is to get the pgd corresponding to the current process and sync it up with the pgd in init_mm(obtained from pgd_offset_k). However, for kernel threads current->mm is NULL and hence pgd = pgd_offset(init_mm, address) = pgd_ref which means the fault handler returns without setting the pgd entry in the MM structure in the context of which the kernel thread has faulted. This could lead to never-ending faults and busy looping of kernel threads like pdflush. So, shouldn't the pgd = pgd_offset(current->mm ?: &init_mm, address); be pgd = pgd_offset(current->active_mm ?: &init_mm, address); We can use active_mm unconditionally because it should be always set. Signed-off-by: Andi Kleen <ak@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/mm/fault.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 9e268b6b204e..90dfae511a41 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -534,7 +534,7 @@ static int vmalloc_fault(unsigned long address)
534 happen within a race in page table update. In the later 534 happen within a race in page table update. In the later
535 case just flush. */ 535 case just flush. */
536 536
537 pgd = pgd_offset(current->mm ?: &init_mm, address); 537 pgd = pgd_offset(current->active_mm, address);
538 pgd_ref = pgd_offset_k(address); 538 pgd_ref = pgd_offset_k(address);
539 if (pgd_none(*pgd_ref)) 539 if (pgd_none(*pgd_ref))
540 return -1; 540 return -1;