linux-cve-announce - CVE-2022-50356: net: sched: sfb: fix null pointer access issue when sfb

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Message-ID: <2025091714-CVE-2022-50356-fe76@gregkh>
Date: Wed, 17 Sep 2025 16:56:15 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-50356: net: sched: sfb: fix null pointer access issue when sfb_init() fails

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

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

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

net: sched: sfb: fix null pointer access issue when sfb_init() fails

When the default qdisc is sfb, if the qdisc of dev_queue fails to be
inited during mqprio_init(), sfb_reset() is invoked to clear resources.
In this case, the q->qdisc is NULL, and it will cause gpf issue.

The process is as follows:
qdisc_create_dflt()
	sfb_init()
		tcf_block_get()          --->failed, q->qdisc is NULL
	...
	qdisc_put()
		...
		sfb_reset()
			qdisc_reset(q->qdisc)    --->q->qdisc is NULL
				ops = qdisc->ops

The following is the Call Trace information:
general protection fault, probably for non-canonical address
0xdffffc0000000003: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
RIP: 0010:qdisc_reset+0x2b/0x6f0
Call Trace:
<TASK>
sfb_reset+0x37/0xd0
qdisc_reset+0xed/0x6f0
qdisc_destroy+0x82/0x4c0
qdisc_put+0x9e/0xb0
qdisc_create_dflt+0x2c3/0x4a0
mqprio_init+0xa71/0x1760
qdisc_create+0x3eb/0x1000
tc_modify_qdisc+0x408/0x1720
rtnetlink_rcv_msg+0x38e/0xac0
netlink_rcv_skb+0x12d/0x3a0
netlink_unicast+0x4a2/0x740
netlink_sendmsg+0x826/0xcc0
sock_sendmsg+0xc5/0x100
____sys_sendmsg+0x583/0x690
___sys_sendmsg+0xe8/0x160
__sys_sendmsg+0xbf/0x160
do_syscall_64+0x35/0x80
entry_SYSCALL_64_after_hwframe+0x46/0xb0
RIP: 0033:0x7f2164122d04
</TASK>

The Linux kernel CVE team has assigned CVE-2022-50356 to this issue.


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

	Issue introduced in 2.6.39 with commit e13e02a3c68d899169c78d9a18689bd73491d59a and fixed in 5.10.152 with commit ded86c4191a3c17f8200d17a7d8a6f63b74554ae
	Issue introduced in 2.6.39 with commit e13e02a3c68d899169c78d9a18689bd73491d59a and fixed in 5.15.76 with commit c2e1e59d59fafe297779ceae1fe0e6fbebc3e745
	Issue introduced in 2.6.39 with commit e13e02a3c68d899169c78d9a18689bd73491d59a and fixed in 6.0.6 with commit 723399af2795fb95687a531c9480464b5f489333
	Issue introduced in 2.6.39 with commit e13e02a3c68d899169c78d9a18689bd73491d59a and fixed in 6.1 with commit 2a3fc78210b9f0e85372a2435368962009f480fc

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-2022-50356
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:
	net/sched/sch_sfb.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/ded86c4191a3c17f8200d17a7d8a6f63b74554ae
	https://git.kernel.org/stable/c/c2e1e59d59fafe297779ceae1fe0e6fbebc3e745
	https://git.kernel.org/stable/c/723399af2795fb95687a531c9480464b5f489333
	https://git.kernel.org/stable/c/2a3fc78210b9f0e85372a2435368962009f480fc