CVE-2026-80738: bpf: Check sk_state before sk_protocol in bpf_tcp_*_syncookie

CVE-2026-80738: bpf: Check sk_state before sk_protocol in bpf_tcp_*_syncookie

[Greg Kroah-Hartman]

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

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

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

bpf: Check sk_state before sk_protocol in bpf_tcp_*_syncookie

bpf_tcp_gen_syncookie and bpf_tcp_check_syncookie accept a socket pointer
'sk' with argument type ARG_PTR_TO_BTF_ID_SOCK_COMMON. However, they access
sk->sk_protocol without validating whether 'sk' represents a full socket.

Fix this issue by checking sk->sk_state != TCP_LISTEN before inspecting
sk->sk_protocol in both bpf_tcp_gen_syncookie and bpf_tcp_check_syncookie.
Since mini-sockets are never in the TCP_LISTEN state, the condition
short-circuits and prevents dereferencing fullsock-specific fields.

The Linux kernel CVE team has assigned CVE-2026-80738 to this issue.


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

	Issue introduced in 5.2 with commit 399040847084a69f345e0a52fd62f04654e0fce3 and fixed in 7.1.9 with commit 23f682083aa3fbc0c49667818efd6979a8bc5ac2
	Issue introduced in 5.2 with commit 399040847084a69f345e0a52fd62f04654e0fce3 and fixed in 7.2 with commit 31a420a822ff92e2090bd5d65efe8e34e2d6d9b8

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-2026-80738
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/filter.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/23f682083aa3fbc0c49667818efd6979a8bc5ac2
	https://git.kernel.org/stable/c/31a420a822ff92e2090bd5d65efe8e34e2d6d9b8