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

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Date:	Mon, 25 Jul 2016 13:56:38 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...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>
Subject: [PATCH 4.4 143/146] tmpfs: dont undo fallocate past its last page

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

------------------

From: Anthony Romano <anthony.romano@...eos.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@...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: Greg Kroah-Hartman <gregkh@...uxfoundation.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;
 		}