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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2010-10-27 15:32:58 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-10-27 18:03:05 -0700
commit20273941f2129aa5a432796d98a276ed73d60782 (patch)
tree85da0d951ac10f239f81ad7f69559fdeb692095b /arch/frv/mm
parenta8e23a291852cd7c4fb5ca696dbb93912185ad10 (diff)
downloadlinux-20273941f2129aa5a432796d98a276ed73d60782.tar.gz
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/frv/mm')
-rw-r--r--arch/frv/mm/highmem.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/frv/mm/highmem.c b/arch/frv/mm/highmem.c
index 61088dcc159..fd7fcd4c2e3 100644
--- a/arch/frv/mm/highmem.c
+++ b/arch/frv/mm/highmem.c
@@ -68,7 +68,7 @@ EXPORT_SYMBOL(__kmap_atomic);
void __kunmap_atomic(void *kvaddr)
{
- int type = kmap_atomic_idx_pop();
+ int type = kmap_atomic_idx();
switch (type) {
case 0: __kunmap_atomic_primary(4, 6); break;
case 1: __kunmap_atomic_primary(5, 7); break;
@@ -83,6 +83,7 @@ void __kunmap_atomic(void *kvaddr)
default:
BUG();
}
+ kmap_atomic_idx_pop();
pagefault_enable();
}
EXPORT_SYMBOL(__kunmap_atomic);