From 20273941f2129aa5a432796d98a276ed73d60782 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 27 Oct 2010 15:32:58 -0700 Subject: 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 Reported-by: Christoph Hellwig Acked-by: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/mn10300/include/asm/highmem.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'arch/mn10300') diff --git a/arch/mn10300/include/asm/highmem.h b/arch/mn10300/include/asm/highmem.h index f577ba2268ca..e2155e686451 100644 --- a/arch/mn10300/include/asm/highmem.h +++ b/arch/mn10300/include/asm/highmem.h @@ -101,7 +101,7 @@ static inline void __kunmap_atomic(unsigned long vaddr) return; } - type = kmap_atomic_idx_pop(); + type = kmap_atomic_idx(); #if HIGHMEM_DEBUG { @@ -119,6 +119,8 @@ static inline void __kunmap_atomic(unsigned long vaddr) __flush_tlb_one(vaddr); } #endif + + kmap_atomic_idx_pop(); pagefault_enable(); } #endif /* __KERNEL__ */ -- cgit v1.2.3