CVE-2022-49879

In the Linux kernel, the following vulnerability has been resolved:

ext4: fix BUG_ON() when directory entry has invalid rec_len

The rec_len field in the directory entry has to be a multiple of 4. A corrupted filesystem image can be used to hit a BUG() in ext4_rec_len_to_disk(), called from make_indexed_dir().

------------[ cut here ]------------ kernel BUG at fs/ext4/ext4.h:2413! ... RIP: 0010:make_indexed_dir+0x53f/0x5f0 ... Call Trace: <TASK> ? add_dirent_to_buf+0x1b2/0x200 ext4_add_entry+0x36e/0x480 ext4_add_nondir+0x2b/0xc0 ext4_create+0x163/0x200 path_openat+0x635/0xe90 do_filp_open+0xb4/0x160 ? __create_object.isra.0+0x1de/0x3b0 ? _raw_spin_unlock+0x12/0x30 do_sys_openat2+0x91/0x150 __x64_sys_open+0x6c/0xa0 do_syscall_64+0x3c/0x80 entry_SYSCALL_64_after_hwframe+0x46/0xb0

The fix simply adds a call to ext4_check_dir_entry() to validate the directory entry, returning -EFSCORRUPTED if the entry is invalid.

This issue in the ext4 filesystem could trigger a kernel panic (BUG_ON()) when encountering a directory entry with a corrupted rec_len field. Such a situation may occur when mounting or manipulating a deliberately malformed or corrupted ext4 image. The kernel previously failed to validate the rec_len value, which must be a multiple of 4. An attacker with the ability to supply or modify ext4 filesystem images (e.g., through removable media or crafted disk images in virtualized environments) could cause a denial of service via kernel crash during directory operations.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.