[PATCH V2] ext4: FIBMAP ioctl causes BUG_ON due to handle EXT_MAX_BLOCKS

[PATCH V2] ext4: FIBMAP ioctl causes BUG_ON due to handle EXT_MAX_BLOCKS

[Kazuya Mio]

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>
---
 fs/ext4/inode.c |    4 ++++
 1 file changed, 4 insertions(+)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 24bfd7f..b0d5860 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);

Re: [PATCH V2] ext4: FIBMAP ioctl causes BUG_ON due to handle EXT_MAX_BLOCKS

[Theodore Ts'o]

On Fri, Apr 04, 2014 at 08:02:58AM +0000, Kazuya Mio wrote:
> 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>

Thanks, applied.

					- Ted