2.6.26 -stable review patch. If anyone has any objections, please let
us know.
------------------
From: Linus Torvalds <torvalds@linux-foundation.org>
commit 94ad374a0751f40d25e22e036c37f7263569d24c upstream
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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
mm/filemap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1778,7 +1778,7 @@ void iov_iter_advance(struct iov_iter *i
* 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);
--
--
