linux-ext4 - [PATCH] ext4: FIBMAP ioctl causes BUG_ON due to handle EXT_MAX

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Date:	Wed, 26 Mar 2014 05:20:54 +0000
From:	Kazuya Mio <k-mio@...jp.nec.com>
To:	"tytso@....edu" <tytso@....edu>,
	"adilger.kernel@...ger.ca" <adilger.kernel@...ger.ca>
CC:	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: [PATCH] ext4: FIBMAP ioctl causes BUG_ON due to handle
 EXT_MAX_BLOCKS

When we try to get 2^32-1 block of the file which has the extent
(ee_block=2^32-2, ee_len=1) with FIBMAP ioctl, it causes BUG_ON
in ext4_ext_put_gap_in_cache().

To avoid the problem, ext4_bmap() needs to check the file logical block number.
ext4_ext_put_gap_in_cache() called via ext4_get_block() cannot handle 2^32-1
because the maximum file logical block number is 2^32-2.
However, the block number in ext4_bmap() which is gotten from user space
is passed to ext4_get_block() directly.

Signed-off-by: Kazuya Mio <k-mio@...jp.nec.com>
---
 fs/ext4/inode.c |    6 ++++++
 1 file changed, 6 insertions(+)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 61d49ff..aef3501 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2873,6 +2873,12 @@ static sector_t ext4_bmap(struct address_space *mapping, sector_t block)
 	if (ext4_has_inline_data(inode))
 		return 0;

+	/*
+	 * We cannot get physical block number over EXT_MAX_BLOCKS
+	 */
+	if ((ext4_lblk_t)block >= EXT_MAX_BLOCKS)
+		return 0;
+
 	if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY) &&
 			test_opt(inode->i_sb, DELALLOC)) {
 		/*

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