linux-cve-announce - CVE-2023-53600: tunnels: fix kasan splat when generating ipv4 pmtu error

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Message-ID: <2025100430-CVE-2023-53600-69ba@gregkh>
Date: Sat,  4 Oct 2025 17:51:54 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53600: tunnels: fix kasan splat when generating ipv4 pmtu error

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

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

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

tunnels: fix kasan splat when generating ipv4 pmtu error

If we try to emit an icmp error in response to a nonliner skb, we get

BUG: KASAN: slab-out-of-bounds in ip_compute_csum+0x134/0x220
Read of size 4 at addr ffff88811c50db00 by task iperf3/1691
CPU: 2 PID: 1691 Comm: iperf3 Not tainted 6.5.0-rc3+ #309
[..]
 kasan_report+0x105/0x140
 ip_compute_csum+0x134/0x220
 iptunnel_pmtud_build_icmp+0x554/0x1020
 skb_tunnel_check_pmtu+0x513/0xb80
 vxlan_xmit_one+0x139e/0x2ef0
 vxlan_xmit+0x1867/0x2760
 dev_hard_start_xmit+0x1ee/0x4f0
 br_dev_queue_push_xmit+0x4d1/0x660
 [..]

ip_compute_csum() cannot deal with nonlinear skbs, so avoid it.
After this change, splat is gone and iperf3 is no longer stuck.

The Linux kernel CVE team has assigned CVE-2023-53600 to this issue.


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

	Issue introduced in 5.9 with commit 4cb47a8644cc9eb8ec81190a50e79e6530d0297f and fixed in 5.10.191 with commit 5850c391fd7e25662334cb3cbf29a62bcbff1084
	Issue introduced in 5.9 with commit 4cb47a8644cc9eb8ec81190a50e79e6530d0297f and fixed in 5.15.127 with commit e95808121953410db8c59f0abfde70ac0d34222c
	Issue introduced in 5.9 with commit 4cb47a8644cc9eb8ec81190a50e79e6530d0297f and fixed in 6.1.46 with commit da5f42a6e7485fbb7a6dbd6a2b3045e19e4df5cc
	Issue introduced in 5.9 with commit 4cb47a8644cc9eb8ec81190a50e79e6530d0297f and fixed in 6.4.11 with commit fe6a9f7516735be9fdabab00e47ef7a3403a174d
	Issue introduced in 5.9 with commit 4cb47a8644cc9eb8ec81190a50e79e6530d0297f and fixed in 6.5 with commit 6a7ac3d20593865209dceb554d8b3f094c6bd940

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-2023-53600
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/ipv4/ip_tunnel_core.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/5850c391fd7e25662334cb3cbf29a62bcbff1084
	https://git.kernel.org/stable/c/e95808121953410db8c59f0abfde70ac0d34222c
	https://git.kernel.org/stable/c/da5f42a6e7485fbb7a6dbd6a2b3045e19e4df5cc
	https://git.kernel.org/stable/c/fe6a9f7516735be9fdabab00e47ef7a3403a174d
	https://git.kernel.org/stable/c/6a7ac3d20593865209dceb554d8b3f094c6bd940