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@sx.jp.nec.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index dc9f0ec..55d4f46 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -481,6 +481,11 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
        ext_debug("ext4_map_blocks(): inode %lu, flag %d, max_blocks %u,"
                  "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;
+
        /*
         * Try to see if we can get the block without requesting a new
         * file system block.