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_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>
Cc: stable@vger.kernel.org

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 5b0d2c7d5408..93f16c5e8a8e 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -522,6 +522,10 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
         if (unlikely(map->m_len > INT_MAX))
                 map->m_len = INT_MAX;
 
+        /* 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);