CVE-2026-74559: xsk: drain continuation descs after overflow in xsk_build_skb()

CVE-2026-74559: xsk: drain continuation descs after overflow in xsk_build_skb()

[Greg Kroah-Hartman]

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

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

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

xsk: drain continuation descs after overflow in xsk_build_skb()

Fix generic xmit path multi-buffer logic when packets are either too big
(count of descriptors exceed MAX_SKB_FRAGS) or an invalid descriptor is
included in fragmented packet. Introduce xdp_sock::drain_cont and act
upon this flag - when it is set, keep on consuming descriptors from
AF_XDP Tx ring and put them directly onto Cq. Previously these
descriptors were silently lost and could never be reached again.

The Linux kernel CVE team has assigned CVE-2026-74559 to this issue.


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

	Issue introduced in 6.6 with commit cf24f5a5feeaae34c1a34d1e04f8ac697290427a and fixed in 6.18.44 with commit ceb00cb87a22c42d20c39336213db2b843ca9e34
	Issue introduced in 6.6 with commit cf24f5a5feeaae34c1a34d1e04f8ac697290427a and fixed in 7.1.8 with commit 5e94d74e4f3baebaa083288f33b4be7ce0a34982
	Issue introduced in 6.6 with commit cf24f5a5feeaae34c1a34d1e04f8ac697290427a and fixed in 7.2-rc6 with commit bd44a6dcd4248883de90f5dad53ae80066e27096

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-2026-74559
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:
	include/net/xdp_sock.h
	net/xdp/xsk.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/ceb00cb87a22c42d20c39336213db2b843ca9e34
	https://git.kernel.org/stable/c/5e94d74e4f3baebaa083288f33b4be7ce0a34982
	https://git.kernel.org/stable/c/bd44a6dcd4248883de90f5dad53ae80066e27096