Entreprise française de cybersécurité depuis 2004
☎ 03 60 47 09 81 - info@securiteinfo.com
☎ 03 60 47 09 81 - info@securiteinfo.com
In the Linux kernel, the following vulnerability has been resolved:ext4: fix double brelse() the buffer of the extents pathIn ext4_ext_try_to_merge_up(), set path[1].p_bh to NULL after it has beenreleased, otherwise it may be released twice. An example of what triggersthis is as follows: split2 map split1|--------|-------|--------|ext4_ext_map_blocks ext4_ext_handle_unwritten_extents ext4_split_convert_extents // path->p_depth == 0 ext4_split_extent // 1. do split1 ext4_split_extent_at |ext4_ext_insert_extent | ext4_ext_create_new_leaf | ext4_ext_grow_indepth | le16_add_cpu(&neh->eh_depth, 1) | ext4_find_extent | // return -ENOMEM |// get error and try zeroout |path = ext4_find_extent | path->p_depth = 1 |ext4_ext_try_to_merge | ext4_ext_try_to_merge_up | path->p_depth = 0 | brelse(path[1].p_bh) ---> not set to NULL here |// zeroout success // 2. update path ext4_find_extent // 3. do split2 ext4_split_extent_at ext4_ext_insert_extent ext4_ext_create_new_leaf ext4_ext_grow_indepth le16_add_cpu(&neh->eh_depth, 1) ext4_find_extent path[0].p_bh = NULL; path->p_depth = 1 read_extent_tree_block ---> return err // path[1].p_bh is still the old value ext4_free_ext_path ext4_ext_drop_refs // path->p_depth == 1 brelse(path[1].p_bh) ---> brelse a buffer twiceFinally got the following WARRNING when removing the buffer from lru:============================================VFS: brelse: Trying to free free bufferWARNING: CPU: 2 PID: 72 at fs/buffer.c:1241 __brelse+0x58/0x90CPU: 2 PID: 72 Comm: kworker/u19:1 Not tainted 6.9.0-dirty #716RIP: 0010:__brelse+0x58/0x90Call Trace:
No PoCs from references.
- https://github.com/w4zu/Debian_security