linux-cve-announce - CVE-2023-53439: net: skb_partial_csum_set() fix against transport header magic value

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Message-ID: <2025091858-CVE-2023-53439-b538@gregkh>
Date: Thu, 18 Sep 2025 18:04:30 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53439: net: skb_partial_csum_set() fix against transport header magic value

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

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

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

net: skb_partial_csum_set() fix against transport header magic value

skb->transport_header uses the special 0xFFFF value
to mark if the transport header was set or not.

We must prevent callers to accidentaly set skb->transport_header
to 0xFFFF. Note that only fuzzers can possibly do this today.

syzbot reported:

WARNING: CPU: 0 PID: 2340 at include/linux/skbuff.h:2847 skb_transport_offset include/linux/skbuff.h:2956 [inline]
WARNING: CPU: 0 PID: 2340 at include/linux/skbuff.h:2847 virtio_net_hdr_to_skb+0xbcc/0x10c0 include/linux/virtio_net.h:103
Modules linked in:
CPU: 0 PID: 2340 Comm: syz-executor.0 Not tainted 6.3.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
RIP: 0010:skb_transport_header include/linux/skbuff.h:2847 [inline]
RIP: 0010:skb_transport_offset include/linux/skbuff.h:2956 [inline]
RIP: 0010:virtio_net_hdr_to_skb+0xbcc/0x10c0 include/linux/virtio_net.h:103
Code: 41 39 df 0f 82 c3 04 00 00 48 8b 7c 24 10 44 89 e6 e8 08 6e 59 ff 48 85 c0 74 54 e8 ce 36 7e fc e9 37 f8 ff ff e8 c4 36 7e fc <0f> 0b e9 93 f8 ff ff 44 89 f7 44 89 e6 e8 32 38 7e fc 45 39 e6 0f
RSP: 0018:ffffc90004497880 EFLAGS: 00010293
RAX: ffffffff84fea55c RBX: 000000000000ffff RCX: ffff888120be2100
RDX: 0000000000000000 RSI: 000000000000ffff RDI: 000000000000ffff
RBP: ffffc90004497990 R08: ffffffff84fe9de5 R09: 0000000000000034
R10: ffffea00048ebd80 R11: 0000000000000034 R12: ffff88811dc2d9c8
R13: dffffc0000000000 R14: ffff88811dc2d9ae R15: 1ffff11023b85b35
FS: 00007f9211a59700(0000) GS:ffff8881f6c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000200002c0 CR3: 00000001215a5000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
packet_snd net/packet/af_packet.c:3076 [inline]
packet_sendmsg+0x4590/0x61a0 net/packet/af_packet.c:3115
sock_sendmsg_nosec net/socket.c:724 [inline]
sock_sendmsg net/socket.c:747 [inline]
__sys_sendto+0x472/0x630 net/socket.c:2144
__do_sys_sendto net/socket.c:2156 [inline]
__se_sys_sendto net/socket.c:2152 [inline]
__x64_sys_sendto+0xe5/0x100 net/socket.c:2152
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x2f/0x50 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f9210c8c169
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f9211a59168 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f9210dabf80 RCX: 00007f9210c8c169
RDX: 000000000000ffed RSI: 00000000200000c0 RDI: 0000000000000003
RBP: 00007f9210ce7ca1 R08: 0000000020000540 R09: 0000000000000014
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffe135d65cf R14: 00007f9211a59300 R15: 0000000000022000

The Linux kernel CVE team has assigned CVE-2023-53439 to this issue.


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

	Issue introduced in 5.19 with commit 66e4c8d950083df8e12981babca788e1635c92b6 and fixed in 6.1.30 with commit 3e785c8deb046305c61b9fa02265d0cb900c4a45
	Issue introduced in 5.19 with commit 66e4c8d950083df8e12981babca788e1635c92b6 and fixed in 6.3.4 with commit 70a76d6816148819d0464f71aafa126c84826628
	Issue introduced in 5.19 with commit 66e4c8d950083df8e12981babca788e1635c92b6 and fixed in 6.4 with commit 424f8416bb39936df6365442d651ee729b283460

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-2023-53439
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/core/skbuff.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/3e785c8deb046305c61b9fa02265d0cb900c4a45
	https://git.kernel.org/stable/c/70a76d6816148819d0464f71aafa126c84826628
	https://git.kernel.org/stable/c/424f8416bb39936df6365442d651ee729b283460