linux-cve-announce - CVE-2022-49526: md/bitmap: don't set sb values if can't pass sanity check

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Message-ID: <2025022612-CVE-2022-49526-5b0b@gregkh>
Date: Wed, 26 Feb 2025 03:13:20 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2022-49526: md/bitmap: don't set sb values if can't pass sanity check

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

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

md/bitmap: don't set sb values if can't pass sanity check

If bitmap area contains invalid data, kernel will crash then mdadm
triggers "Segmentation fault".
This is cluster-md speical bug. In non-clustered env, mdadm will
handle broken metadata case. In clustered array, only kernel space
handles bitmap slot info. But even this bug only happened in clustered
env, current sanity check is wrong, the code should be changed.

How to trigger: (faulty injection)

dd if=/dev/zero bs=1M count=1 oflag=direct of=/dev/sda
dd if=/dev/zero bs=1M count=1 oflag=direct of=/dev/sdb
mdadm -C /dev/md0 -b clustered -e 1.2 -n 2 -l mirror /dev/sda /dev/sdb
mdadm -Ss
echo aaa > magic.txt
 == below modifying slot 2 bitmap data ==
dd if=magic.txt of=/dev/sda seek=16384 bs=1 count=3 <== destroy magic
dd if=/dev/zero of=/dev/sda seek=16436 bs=1 count=4 <== ZERO chunksize
mdadm -A /dev/md0 /dev/sda /dev/sdb
 == kernel crashes. mdadm outputs "Segmentation fault" ==

Reason of kernel crash:

In md_bitmap_read_sb (called by md_bitmap_create), bad bitmap magic didn't
block chunksize assignment, and zero value made DIV_ROUND_UP_SECTOR_T()
trigger "divide error".

Crash log:

kernel: md: md0 stopped.
kernel: md/raid1:md0: not clean -- starting background reconstruction
kernel: md/raid1:md0: active with 2 out of 2 mirrors
kernel: dlm: ... ...
kernel: md-cluster: Joined cluster 44810aba-38bb-e6b8-daca-bc97a0b254aa slot 1
kernel: md0: invalid bitmap file superblock: bad magic
kernel: md_bitmap_copy_from_slot can't get bitmap from slot 2
kernel: md-cluster: Could not gather bitmaps from slot 2
kernel: divide error: 0000 [#1] SMP NOPTI
kernel: CPU: 0 PID: 1603 Comm: mdadm Not tainted 5.14.6-1-default
kernel: Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
kernel: RIP: 0010:md_bitmap_create+0x1d1/0x850 [md_mod]
kernel: RSP: 0018:ffffc22ac0843ba0 EFLAGS: 00010246
kernel: ... ...
kernel: Call Trace:
kernel:  ? dlm_lock_sync+0xd0/0xd0 [md_cluster 77fe..7a0]
kernel:  md_bitmap_copy_from_slot+0x2c/0x290 [md_mod 24ea..d3a]
kernel:  load_bitmaps+0xec/0x210 [md_cluster 77fe..7a0]
kernel:  md_bitmap_load+0x81/0x1e0 [md_mod 24ea..d3a]
kernel:  do_md_run+0x30/0x100 [md_mod 24ea..d3a]
kernel:  md_ioctl+0x1290/0x15a0 [md_mod 24ea....d3a]
kernel:  ? mddev_unlock+0xaa/0x130 [md_mod 24ea..d3a]
kernel:  ? blkdev_ioctl+0xb1/0x2b0
kernel:  block_ioctl+0x3b/0x40
kernel:  __x64_sys_ioctl+0x7f/0xb0
kernel:  do_syscall_64+0x59/0x80
kernel:  ? exit_to_user_mode_prepare+0x1ab/0x230
kernel:  ? syscall_exit_to_user_mode+0x18/0x40
kernel:  ? do_syscall_64+0x69/0x80
kernel:  entry_SYSCALL_64_after_hwframe+0x44/0xae
kernel: RIP: 0033:0x7f4a15fa722b
kernel: ... ...
kernel: ---[ end trace 8afa7612f559c868 ]---
kernel: RIP: 0010:md_bitmap_create+0x1d1/0x850 [md_mod]

The Linux kernel CVE team has assigned CVE-2022-49526 to this issue.


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

	Fixed in 4.19.247 with commit 422e8f7ba1e08c8e0e88d375bcb550bc2bbfe96d
	Fixed in 5.4.198 with commit 0959aa00f9765bd8c654b1365012e41b51c733cc
	Fixed in 5.10.121 with commit e69e93120f6219b9cc4fba3b515b6ababd8548aa
	Fixed in 5.15.46 with commit 27f672af28a8e9b783ff7f0eaf7ef2fbd5a2f4ba
	Fixed in 5.17.14 with commit cf9392282a2cf5a8d83dd1c5aa1a097e12f172bc
	Fixed in 5.18.3 with commit d8f1558e1daf54f53a90b4c5700ae3e3a4b13412
	Fixed in 5.19 with commit e68cb83a57a458b01c9739e2ad9cb70b04d1e6d2

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-2022-49526
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:
	drivers/md/md-bitmap.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/422e8f7ba1e08c8e0e88d375bcb550bc2bbfe96d
	https://git.kernel.org/stable/c/0959aa00f9765bd8c654b1365012e41b51c733cc
	https://git.kernel.org/stable/c/e69e93120f6219b9cc4fba3b515b6ababd8548aa
	https://git.kernel.org/stable/c/27f672af28a8e9b783ff7f0eaf7ef2fbd5a2f4ba
	https://git.kernel.org/stable/c/cf9392282a2cf5a8d83dd1c5aa1a097e12f172bc
	https://git.kernel.org/stable/c/d8f1558e1daf54f53a90b4c5700ae3e3a4b13412
	https://git.kernel.org/stable/c/e68cb83a57a458b01c9739e2ad9cb70b04d1e6d2