CVE-2022-49879: ext4: fix BUG_ON() when directory entry has invalid rec_len

CVE-2022-49879: ext4: fix BUG_ON() when directory entry has invalid rec_len

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

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.

The Linux kernel CVE team has assigned CVE-2022-49879 to this issue.


Affected and fixed versions
===========================

	Fixed in 5.4.224 with commit 2fa24d0274fbf913b56ee31f15bc01168669d909
	Fixed in 5.10.154 with commit 156451a67b93986fb07c274ef6995ff40766c5ad
	Fixed in 5.15.78 with commit 999cff2b6ce3b45c08abf793bf55534777421327
	Fixed in 6.0.8 with commit ce1ee2c8827fb6493e91acbd50f664cf2a972c3d
	Fixed in 6.1 with commit 17a0bc9bd697f75cfdf9b378d5eb2d7409c91340

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2022-49879
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	fs/ext4/namei.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/2fa24d0274fbf913b56ee31f15bc01168669d909
	https://git.kernel.org/stable/c/156451a67b93986fb07c274ef6995ff40766c5ad
	https://git.kernel.org/stable/c/999cff2b6ce3b45c08abf793bf55534777421327
	https://git.kernel.org/stable/c/ce1ee2c8827fb6493e91acbd50f664cf2a972c3d
	https://git.kernel.org/stable/c/17a0bc9bd697f75cfdf9b378d5eb2d7409c91340