linux-cve-announce - CVE-2022-50655: ppp: associate skb with a device at tx

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Message-ID: <2025120938-CVE-2022-50655-746b@gregkh>
Date: Tue,  9 Dec 2025 09:01:56 +0900
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-50655: ppp: associate skb with a device at tx

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

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

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

ppp: associate skb with a device at tx

Syzkaller triggered flow dissector warning with the following:

r0 = openat$ppp(0xffffffffffffff9c, &(0x7f0000000000), 0xc0802, 0x0)
ioctl$PPPIOCNEWUNIT(r0, 0xc004743e, &(0x7f00000000c0))
ioctl$PPPIOCSACTIVE(r0, 0x40107446, &(0x7f0000000240)={0x2, &(0x7f0000000180)=[{0x20, 0x0, 0x0, 0xfffff034}, {0x6}]})
pwritev(r0, &(0x7f0000000040)=[{&(0x7f0000000140)='\x00!', 0x2}], 0x1, 0x0, 0x0)

[    9.485814] WARNING: CPU: 3 PID: 329 at net/core/flow_dissector.c:1016 __skb_flow_dissect+0x1ee0/0x1fa0
[    9.485929]  skb_get_poff+0x53/0xa0
[    9.485937]  bpf_skb_get_pay_offset+0xe/0x20
[    9.485944]  ? ppp_send_frame+0xc2/0x5b0
[    9.485949]  ? _raw_spin_unlock_irqrestore+0x40/0x60
[    9.485958]  ? __ppp_xmit_process+0x7a/0xe0
[    9.485968]  ? ppp_xmit_process+0x5b/0xb0
[    9.485974]  ? ppp_write+0x12a/0x190
[    9.485981]  ? do_iter_write+0x18e/0x2d0
[    9.485987]  ? __import_iovec+0x30/0x130
[    9.485997]  ? do_pwritev+0x1b6/0x240
[    9.486016]  ? trace_hardirqs_on+0x47/0x50
[    9.486023]  ? __x64_sys_pwritev+0x24/0x30
[    9.486026]  ? do_syscall_64+0x3d/0x80
[    9.486031]  ? entry_SYSCALL_64_after_hwframe+0x63/0xcd

Flow dissector tries to find skb net namespace either via device
or via socket. Neigher is set in ppp_send_frame, so let's manually
use ppp->dev.

The Linux kernel CVE team has assigned CVE-2022-50655 to this issue.


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

	Fixed in 4.9.337 with commit e387a25552951802102e279931d6f7dd2ecc34c1
	Fixed in 4.14.303 with commit 30f186978e87bef2f22ed349010d3e23271e8d44
	Fixed in 4.19.270 with commit c2a698ff156974908308f42cf5991ab5c0c4b8cd
	Fixed in 5.4.229 with commit 7da524781c531ebaf2f94c9dc4c541b82edecfed
	Fixed in 5.10.163 with commit 148dcbd3af039ae39c3af697a3183008c7995805
	Fixed in 5.15.86 with commit 4b8f3b939266c90f03b7cc7e26a4c28c7b64137b
	Fixed in 6.0.16 with commit 18dc946360bfe0de016a59e3cc3ee1f450fceb9d
	Fixed in 6.1.2 with commit ee678b1f52f9439e930db2db3fd7e345d03e1a50
	Fixed in 6.2 with commit 9f225444467b98579cf28d94f4ad053460dfdb84

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-2022-50655
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/net/ppp/ppp_generic.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/e387a25552951802102e279931d6f7dd2ecc34c1
	https://git.kernel.org/stable/c/30f186978e87bef2f22ed349010d3e23271e8d44
	https://git.kernel.org/stable/c/c2a698ff156974908308f42cf5991ab5c0c4b8cd
	https://git.kernel.org/stable/c/7da524781c531ebaf2f94c9dc4c541b82edecfed
	https://git.kernel.org/stable/c/148dcbd3af039ae39c3af697a3183008c7995805
	https://git.kernel.org/stable/c/4b8f3b939266c90f03b7cc7e26a4c28c7b64137b
	https://git.kernel.org/stable/c/18dc946360bfe0de016a59e3cc3ee1f450fceb9d
	https://git.kernel.org/stable/c/ee678b1f52f9439e930db2db3fd7e345d03e1a50
	https://git.kernel.org/stable/c/9f225444467b98579cf28d94f4ad053460dfdb84