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

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Message-Id: <1462713387-16724-1-git-send-email-anthony.romano@coreos.com>
Date:	Sun,  8 May 2016 06:16:27 -0700
From:	Anthony Romano <anthony.romano@...eos.com>
To:	hughd@...gle.com
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Anthony Romano <anthony.romano@...eos.com>
Subject: [PATCH] tmpfs: don't undo fallocate past its last page

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.

Signed-off-by: Anthony Romano <anthony.romano@...eos.com>
---
 mm/shmem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 719bd6b..f0f9405 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2238,7 +2238,7 @@ 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_SHIFT,
-				(loff_t)index << PAGE_SHIFT, true);
+				((loff_t)index << PAGE_SHIFT) - 1, true);
 			goto undone;
 		}
 
-- 
2.8.1