diff options
authorLinus Torvalds <torvalds@linux-foundation.org>2008-07-30 14:45:12 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-30 14:50:18 -0700
commit94ad374a0751f40d25e22e036c37f7263569d24c (patch)
parent0056e65f9e28d83ee1a3fb4f7d0041e838f03c34 (diff)
Fix off-by-one error in iov_iter_advance()
The iov_iter_advance() function would look at the iov->iov_len entry even though it might have iterated over the whole array, and iov was pointing past the end. This would cause DEBUG_PAGEALLOC to trigger a kernel page fault if the allocation was at the end of a page, and the next page was unallocated. The quick fix is to just change the order of the tests: check that there is any iovec data left before we check the iov entry itself. Thanks to Alexey Dobriyan for finding this case, and testing the fix. Reported-and-tested-by: Alexey Dobriyan <adobriyan@gmail.com> Cc: Nick Piggin <npiggin@suse.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: <stable@kernel.org> [2.6.25.x, 2.6.26.x] Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index 42bbc6909ba4..d97d1ad55473 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1879,7 +1879,7 @@ void iov_iter_advance(struct iov_iter *i, size_t bytes)
* The !iov->iov_len check ensures we skip over unlikely
* zero-length segments (without overruning the iovec).
- while (bytes || unlikely(!iov->iov_len && i->count)) {
+ while (bytes || unlikely(i->count && !iov->iov_len)) {
int copy;
copy = min(bytes, iov->iov_len - base);

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