linux-cve-announce - CVE-2022-49707: ext4: add reserved GDT blocks check

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Message-ID: <2025022630-CVE-2022-49707-c4b7@gregkh>
Date: Wed, 26 Feb 2025 03:24:30 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2022-49707: ext4: add reserved GDT blocks check

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

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

ext4: add reserved GDT blocks check

We capture a NULL pointer issue when resizing a corrupt ext4 image which
is freshly clear resize_inode feature (not run e2fsck). It could be
simply reproduced by following steps. The problem is because of the
resize_inode feature was cleared, and it will convert the filesystem to
meta_bg mode in ext4_resize_fs(), but the es->s_reserved_gdt_blocks was
not reduced to zero, so could we mistakenly call reserve_backup_gdb()
and passing an uninitialized resize_inode to it when adding new group
descriptors.

 mkfs.ext4 /dev/sda 3G
 tune2fs -O ^resize_inode /dev/sda #forget to run requested e2fsck
 mount /dev/sda /mnt
 resize2fs /dev/sda 8G

 ========
 BUG: kernel NULL pointer dereference, address: 0000000000000028
 CPU: 19 PID: 3243 Comm: resize2fs Not tainted 5.18.0-rc7-00001-gfde086c5ebfd #748
 ...
 RIP: 0010:ext4_flex_group_add+0xe08/0x2570
 ...
 Call Trace:
  <TASK>
  ext4_resize_fs+0xbec/0x1660
  __ext4_ioctl+0x1749/0x24e0
  ext4_ioctl+0x12/0x20
  __x64_sys_ioctl+0xa6/0x110
  do_syscall_64+0x3b/0x90
  entry_SYSCALL_64_after_hwframe+0x44/0xae
 RIP: 0033:0x7f2dd739617b
 ========

The fix is simple, add a check in ext4_resize_begin() to make sure that
the es->s_reserved_gdt_blocks is zero when the resize_inode feature is
disabled.

The Linux kernel CVE team has assigned CVE-2022-49707 to this issue.


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

	Fixed in 4.9.320 with commit 0dc2fca8e4f9ac4a40e8424a10163369cca0cc06
	Fixed in 4.14.285 with commit 7c921328ac760bba780bdace41f4cd045f7f1405
	Fixed in 4.19.249 with commit b9747263b13e5290ac4d63bec47e38f701303cad
	Fixed in 5.4.200 with commit fba54289176702a7caac0b64738406775817f451
	Fixed in 5.10.124 with commit bfd004a1d3a062aac300523d406ac1f3e5f1a82c
	Fixed in 5.15.49 with commit 33b1bba31f4c784d33d2c2517964bdccdc9204cd
	Fixed in 5.18.6 with commit af75c481a2e45e70f62f5942c93695e95bf7bd21
	Fixed in 5.19 with commit b55c3cd102a6f48b90e61c44f7f3dda8c290c694

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-2022-49707
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/resize.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/0dc2fca8e4f9ac4a40e8424a10163369cca0cc06
	https://git.kernel.org/stable/c/7c921328ac760bba780bdace41f4cd045f7f1405
	https://git.kernel.org/stable/c/b9747263b13e5290ac4d63bec47e38f701303cad
	https://git.kernel.org/stable/c/fba54289176702a7caac0b64738406775817f451
	https://git.kernel.org/stable/c/bfd004a1d3a062aac300523d406ac1f3e5f1a82c
	https://git.kernel.org/stable/c/33b1bba31f4c784d33d2c2517964bdccdc9204cd
	https://git.kernel.org/stable/c/af75c481a2e45e70f62f5942c93695e95bf7bd21
	https://git.kernel.org/stable/c/b55c3cd102a6f48b90e61c44f7f3dda8c290c694