linux-kernel - [PATCH 3.12 028/100] tmpfs: don't undo fallocate past its last page

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Date:   Fri, 19 Aug 2016 09:10:27 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Anthony Romano <anthony.romano@...eos.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Hugh Dickins <hughd@...gle.com>,
        Brandon Philips <brandon@...p.co>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 028/100] tmpfs: don't undo fallocate past its last page

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

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

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@...eos.com>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Brandon Philips <brandon@...p.co>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 mm/shmem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index e9502a67e300..ff42f161fc32 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1897,7 +1897,7 @@ 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;
 		}
 
-- 
2.9.3