[PATCH 4.4 143/146] tmpfs: dont undo fallocate past its last page

Greg Kroah-Hartman
2016-07-25T21:19:12Z

From: Anthony Romano <anthony.romano@coreos.com>

commit b9b4bb26af017dbe930cd4df7f9b2fc3a0497bfe upstream.

When fallocate is interrupted it will undo a range that extends one byte
past its range of allocated pages. This can corrupt an in-use page by
zeroing out its first byte. Instead, undo using the inclusive byte
range.

Fixes: 1635f6a74152f1d ("tmpfs: undo fallocation on failure")
Link: http://lkml.kernel.org/r/1462713387-16724-1-git-send-email-anthony.romano@coreos.com
Signed-off-by: Anthony Romano <anthony.romano@coreos.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Brandon Philips <brandon@ifup.co>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
mm/shmem.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2155,7 +2155,7 @@ static long shmem_fallocate(struct file
/* Remove the !PageUptodate pages we added */
shmem_undo_range(inode,
(loff_t)start << PAGE_CACHE_SHIFT,
- (loff_t)index << PAGE_CACHE_SHIFT, true);
+ ((loff_t)index << PAGE_CACHE_SHIFT) - 1, true);
goto undone;
}