[PATCH 3.10 045/180] tmpfs: don't undo fallocate past its last page

[Willy Tarreau]

From: Anthony Romano <anthony.romano@xxxxxxxxxx>

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@xxxxxxxxxx
Signed-off-by: Anthony Romano <anthony.romano@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Brandon Philips <brandon@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
---
 mm/shmem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 4e4a734..e163e40 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1950,7 +1950,7 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
 			/* 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;
 		}
 
-- 
2.8.0.rc2.1.gbe9624a