linux-kernel - [PATCH] fs/buffer.c: grow_buffers: fix the uncorrect check

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Date:	Sun, 01 Jun 2014 02:12:05 +0800
From:	mnipxh <mnipxh@...il.com>
To:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	viro@...iv.linux.org.uk
CC:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	yanmin_zhang@...ux.intel.com, shuox.liu@...el.com
Subject: [PATCH] fs/buffer.c: grow_buffers: fix the uncorrect check

When pgoff_t index is 32bit, sector_t block is 64bit, need check if block number is too big.
If block is bigger than (4Gb * PAGE_SIZE), index becomes a wrong value.
Commit e5657933863f43cc6bb76a54d659303dafaa9e58 wants to do this. But it gives an uncorrect check.
I think block != index << sizebits is correct. And it can detect such issue above.

Signed-off-by: xinhui.pan <xinhuix.pan@...el.com>
---
 fs/buffer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 9ddb9fc..1a674a6 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1081,7 +1081,7 @@ grow_buffers(struct block_device *bdev, sector_t block, int size)
 	 * Check for a block which wants to lie outside our maximum possible
 	 * pagecache index.  (this comparison is done using sector_t types).
 	 */
-	if (unlikely(index != block >> sizebits)) {
+	if (unlikely(block != index << sizebits)) {
 		char b[BDEVNAME_SIZE];
 
 		printk(KERN_ERR "%s: requested out-of-range block %llu for "
-- 
1.9.1
--
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