diff options
author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2010-10-27 18:32:58 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-10-27 21:03:05 -0400 |
commit | 20273941f2129aa5a432796d98a276ed73d60782 (patch) | |
tree | 85da0d951ac10f239f81ad7f69559fdeb692095b /arch/mips/mm | |
parent | a8e23a291852cd7c4fb5ca696dbb93912185ad10 (diff) |
mm: fix race in kunmap_atomic()
Christoph reported a nice splat which illustrated a race in the new stack
based kmap_atomic implementation.
The problem is that we pop our stack slot before we're completely done
resetting its state -- in particular clearing the PTE (sometimes that's
CONFIG_DEBUG_HIGHMEM). If an interrupt happens before we actually clear
the PTE used for the last slot, that interrupt can reuse the slot in a
dirty state, which triggers a BUG in kmap_atomic().
Fix this by introducing kmap_atomic_idx() which reports the current slot
index without actually releasing it and use that to find the PTE and delay
the _pop() until after we're completely done.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reported-by: Christoph Hellwig <hch@infradead.org>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/mips/mm')
-rw-r--r-- | arch/mips/mm/highmem.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/mips/mm/highmem.c b/arch/mips/mm/highmem.c index 1e69b1fb4b85..3634c7ea06ac 100644 --- a/arch/mips/mm/highmem.c +++ b/arch/mips/mm/highmem.c | |||
@@ -74,7 +74,7 @@ void __kunmap_atomic(void *kvaddr) | |||
74 | return; | 74 | return; |
75 | } | 75 | } |
76 | 76 | ||
77 | type = kmap_atomic_idx_pop(); | 77 | type = kmap_atomic_idx(); |
78 | #ifdef CONFIG_DEBUG_HIGHMEM | 78 | #ifdef CONFIG_DEBUG_HIGHMEM |
79 | { | 79 | { |
80 | int idx = type + KM_TYPE_NR * smp_processor_id(); | 80 | int idx = type + KM_TYPE_NR * smp_processor_id(); |
@@ -89,6 +89,7 @@ void __kunmap_atomic(void *kvaddr) | |||
89 | local_flush_tlb_one(vaddr); | 89 | local_flush_tlb_one(vaddr); |
90 | } | 90 | } |
91 | #endif | 91 | #endif |
92 | kmap_atomic_idx_pop(); | ||
92 | pagefault_enable(); | 93 | pagefault_enable(); |
93 | } | 94 | } |
94 | EXPORT_SYMBOL(__kunmap_atomic); | 95 | EXPORT_SYMBOL(__kunmap_atomic); |