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Message-ID: <2025022627-CVE-2022-49689-06fb@gregkh>
Date: Wed, 26 Feb 2025 03:24:12 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2022-49689: xen-blkfront: Handle NULL gendisk
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
xen-blkfront: Handle NULL gendisk
When a VBD is not fully created and then closed, the kernel can have a
NULL pointer dereference:
The reproducer is trivial:
[user@...0 ~]$ sudo xl block-attach work backend=sys-usb vdev=xvdi target=/dev/sdz
[user@...0 ~]$ xl block-list work
Vdev BE handle state evt-ch ring-ref BE-path
51712 0 241 4 -1 -1 /local/domain/0/backend/vbd/241/51712
51728 0 241 4 -1 -1 /local/domain/0/backend/vbd/241/51728
51744 0 241 4 -1 -1 /local/domain/0/backend/vbd/241/51744
51760 0 241 4 -1 -1 /local/domain/0/backend/vbd/241/51760
51840 3 241 3 -1 -1 /local/domain/3/backend/vbd/241/51840
^ note state, the /dev/sdz doesn't exist in the backend
[user@...0 ~]$ sudo xl block-detach work xvdi
[user@...0 ~]$ xl block-list work
Vdev BE handle state evt-ch ring-ref BE-path
work is an invalid domain identifier
And its console has:
BUG: kernel NULL pointer dereference, address: 0000000000000050
PGD 80000000edebb067 P4D 80000000edebb067 PUD edec2067 PMD 0
Oops: 0000 [#1] PREEMPT SMP PTI
CPU: 1 PID: 52 Comm: xenwatch Not tainted 5.16.18-2.43.fc32.qubes.x86_64 #1
RIP: 0010:blk_mq_stop_hw_queues+0x5/0x40
Code: 00 48 83 e0 fd 83 c3 01 48 89 85 a8 00 00 00 41 39 5c 24 50 77 c0 5b 5d 41 5c 41 5d c3 c3 0f 1f 80 00 00 00 00 0f 1f 44 00 00 <8b> 47 50 85 c0 74 32 41 54 49 89 fc 55 53 31 db 49 8b 44 24 48 48
RSP: 0018:ffffc90000bcfe98 EFLAGS: 00010293
RAX: ffffffffc0008370 RBX: 0000000000000005 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000005 RDI: 0000000000000000
RBP: ffff88800775f000 R08: 0000000000000001 R09: ffff888006e620b8
R10: ffff888006e620b0 R11: f000000000000000 R12: ffff8880bff39000
R13: ffff8880bff39000 R14: 0000000000000000 R15: ffff88800604be00
FS: 0000000000000000(0000) GS:ffff8880f3300000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000050 CR3: 00000000e932e002 CR4: 00000000003706e0
Call Trace:
<TASK>
blkback_changed+0x95/0x137 [xen_blkfront]
? read_reply+0x160/0x160
xenwatch_thread+0xc0/0x1a0
? do_wait_intr_irq+0xa0/0xa0
kthread+0x16b/0x190
? set_kthread_struct+0x40/0x40
ret_from_fork+0x22/0x30
</TASK>
Modules linked in: snd_seq_dummy snd_hrtimer snd_seq snd_seq_device snd_timer snd soundcore ipt_REJECT nf_reject_ipv4 xt_state xt_conntrack nft_counter nft_chain_nat xt_MASQUERADE nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nft_compat nf_tables nfnetlink intel_rapl_msr intel_rapl_common crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel xen_netfront pcspkr xen_scsiback target_core_mod xen_netback xen_privcmd xen_gntdev xen_gntalloc xen_blkback xen_evtchn ipmi_devintf ipmi_msghandler fuse bpf_preload ip_tables overlay xen_blkfront
CR2: 0000000000000050
---[ end trace 7bc9597fd06ae89d ]---
RIP: 0010:blk_mq_stop_hw_queues+0x5/0x40
Code: 00 48 83 e0 fd 83 c3 01 48 89 85 a8 00 00 00 41 39 5c 24 50 77 c0 5b 5d 41 5c 41 5d c3 c3 0f 1f 80 00 00 00 00 0f 1f 44 00 00 <8b> 47 50 85 c0 74 32 41 54 49 89 fc 55 53 31 db 49 8b 44 24 48 48
RSP: 0018:ffffc90000bcfe98 EFLAGS: 00010293
RAX: ffffffffc0008370 RBX: 0000000000000005 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000005 RDI: 0000000000000000
RBP: ffff88800775f000 R08: 0000000000000001 R09: ffff888006e620b8
R10: ffff888006e620b0 R11: f000000000000000 R12: ffff8880bff39000
R13: ffff8880bff39000 R14: 0000000000000000 R15: ffff88800604be00
FS: 0000000000000000(0000) GS:ffff8880f3300000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000050 CR3: 00000000e932e002 CR4: 00000000003706e0
Kernel panic - not syncing: Fatal exception
Kernel Offset: disabled
info->rq and info->gd are only set in blkfront_connect(), which is
called for state 4 (XenbusStateConnected). Guard against using NULL
variables in blkfront_closing() to avoid the issue.
The rest of blkfront_closing looks okay. If info->nr_rings is 0, then
for_each_rinfo won't do anything.
blkfront_remove also needs to check for non-NULL pointers before
cleaning up the gendisk and request queue.
The Linux kernel CVE team has assigned CVE-2022-49689 to this issue.
Affected and fixed versions
===========================
Issue introduced in 5.14 with commit 05d69d950d9d84218fc9beafd02dea1f6a70e09e and fixed in 5.15.51 with commit ffa12a326415dfe5fc21e66d9d2b86896b4c9eaf
Issue introduced in 5.14 with commit 05d69d950d9d84218fc9beafd02dea1f6a70e09e and fixed in 5.18.8 with commit db403bc872af09360f5c80f83dc3b360f0be49af
Issue introduced in 5.14 with commit 05d69d950d9d84218fc9beafd02dea1f6a70e09e and fixed in 5.19 with commit f9710c357e5bbf64d7ce45ba0bc75a52222491c1
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-2022-49689
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/block/xen-blkfront.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/ffa12a326415dfe5fc21e66d9d2b86896b4c9eaf
https://git.kernel.org/stable/c/db403bc872af09360f5c80f83dc3b360f0be49af
https://git.kernel.org/stable/c/f9710c357e5bbf64d7ce45ba0bc75a52222491c1
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