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author | 2010-10-27 15:32:58 -0700 | |
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committer | 2010-10-27 18:03:05 -0700 | |
commit | 20273941f2129aa5a432796d98a276ed73d60782 (patch) | |
tree | 85da0d951ac10f239f81ad7f69559fdeb692095b /arch/x86/mm/iomap_32.c | |
parent | mm,x86: fix kmap_atomic_push vs ioremap_32.c (diff) | |
download | linux-20273941f2129aa5a432796d98a276ed73d60782.tar.gz linux-20273941f2129aa5a432796d98a276ed73d60782.tar.bz2 linux-20273941f2129aa5a432796d98a276ed73d60782.zip |
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/x86/mm/iomap_32.c')
-rw-r--r-- | arch/x86/mm/iomap_32.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/mm/iomap_32.c b/arch/x86/mm/iomap_32.c index 75a3d7f24a2c..7b179b499fa3 100644 --- a/arch/x86/mm/iomap_32.c +++ b/arch/x86/mm/iomap_32.c @@ -98,7 +98,7 @@ iounmap_atomic(void __iomem *kvaddr) vaddr <= __fix_to_virt(FIX_KMAP_BEGIN)) { int idx, type; - type = kmap_atomic_idx_pop(); + type = kmap_atomic_idx(); idx = type + KM_TYPE_NR * smp_processor_id(); #ifdef CONFIG_DEBUG_HIGHMEM @@ -111,6 +111,7 @@ iounmap_atomic(void __iomem *kvaddr) * attributes or becomes a protected page in a hypervisor. */ kpte_clear_flush(kmap_pte-idx, vaddr); + kmap_atomic_idx_pop(); } pagefault_enable(); |