[PATCH] fs: Do to trim high file position bits in iomap_page_mkwrite_actor

From: Jan Kara <jack@suse.cz>
To: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>,
	linux-fsdevel@vger.kernel.org, Jan Kara <jack@suse.cz>
Subject: [PATCH] fs: Do to trim high file position bits in iomap_page_mkwrite_actor
Date: Thu, 20 Oct 2016 13:35:42 +0200	[thread overview]
Message-ID: <1476963342-26989-1-git-send-email-jack@suse.cz> (raw)

iomap_page_mkwrite_actor() calls __block_write_begin_int() with position
masked as pos & ~PAGE_MASK which is equivalent to pos & (PAGE_SIZE-1).
Thus it masks off high bits of file position. However
__block_write_begin_int() expects full file position on input. This does
not cause any visible issues because all __block_write_begin_int()
really cares about are low file position bits but still it is a bug
waiting to happen.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/iomap.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/iomap.c b/fs/iomap.c
index 013d1d36fbbf..3341907eefc7 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -433,8 +433,7 @@ iomap_page_mkwrite_actor(struct inode *inode, loff_t pos, loff_t length,
 	struct page *page = data;
 	int ret;
 
-	ret = __block_write_begin_int(page, pos & ~PAGE_MASK, length,
-			NULL, iomap);
+	ret = __block_write_begin_int(page, pos, length, NULL, iomap);
 	if (ret)
 		return ret;
 
-- 
2.6.6

