[3.11.y.z extended stable] Patch "ext4: FIBMAP ioctl causes BUG_ON due to handle EXT_MAX_BLOCKS" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    ext4: FIBMAP ioctl causes BUG_ON due to handle EXT_MAX_BLOCKS

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From fe920f3d208dec13b71935a4b91b4bbae384ba78 Mon Sep 17 00:00:00 2001
From: Kazuya Mio <k-mio at sx.jp.nec.com>
Date: Mon, 7 Apr 2014 10:53:28 -0400
Subject: ext4: FIBMAP ioctl causes BUG_ON due to handle EXT_MAX_BLOCKS

commit 4adb6ab3e0fa71363a5ef229544b2d17de6600d7 upstream.

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_map_blocks() needs to check the file logical block
number. ext4_ext_put_gap_in_cache() called via ext4_map_blocks() cannot
handle 2^32-1 because the maximum file logical block number is 2^32-2.

Note that ext4_ind_map_blocks() returns -EIO when the block number is invalid.
So ext4_map_blocks() should also return the same errno.

Signed-off-by: Kazuya Mio <k-mio at sx.jp.nec.com>
Signed-off-by: "Theodore Ts'o" <tytso at mit.edu>
[ luis: backported to 3.11: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/ext4/inode.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index e2dc5c4..6582dd6 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -515,6 +515,10 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
 		  "logical block %lu\n", inode->i_ino, flags, map->m_len,
 		  (unsigned long) map->m_lblk);

+	/* We can handle the block number less than EXT_MAX_BLOCKS */
+	if (unlikely(map->m_lblk >= EXT_MAX_BLOCKS))
+		return -EIO;
+
 	/* Lookup extent status tree firstly */
 	if (ext4_es_lookup_extent(inode, map->m_lblk, &es)) {
 		ext4_es_lru_add(inode);
--
1.9.1