CVE-2026-74662: inet: frags: publish queues before arming timer

From: Greg Kroah-Hartman <[email protected]>

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

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

inet: frags: publish queues before arming timer

inet_frag_create() arms the fragment queue timer before inserting the
queue into the fqdir rhashtable. If the namespace fragment timeout is
zero or negative, the timer can run before the queue is published.

The timer callback then marks the queue complete, tries to remove a node
that is not in the hash table yet, and drops the anticipated hash
reference. Creation can subsequently publish the completed queue without
restoring that reference, leaving a stale hash node after the caller drops
the remaining reference.

Publish the queue first and arm the timer while holding the queue lock.
This makes timer expiry wait until the queue is visible in the hash table,
so inet_frag_kill() can remove the node and balance the hash reference.

The Linux kernel CVE team has assigned CVE-2026-74662 to this issue.


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

	Issue introduced in 4.17 with commit 648700f76b03b7e8149d13cc2bdb3355035258a9 and fixed in 6.18.45 with commit 9f904dd3e455750e5d4ec9b2f134835811b85a2f
	Issue introduced in 4.17 with commit 648700f76b03b7e8149d13cc2bdb3355035258a9 and fixed in 7.1.9 with commit 928128865e43b197e30688dc1bc991592c97edcf
	Issue introduced in 4.17 with commit 648700f76b03b7e8149d13cc2bdb3355035258a9 and fixed in 7.2 with commit 653d7ddf6cba867777a3d14c4f83ace008c5ad13
	Issue introduced in 4.4.174 with commit 493107105843f299662b3b664a83804645564f12

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-2026-74662
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/inet_fragment.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/9f904dd3e455750e5d4ec9b2f134835811b85a2f
	https://git.kernel.org/stable/c/928128865e43b197e30688dc1bc991592c97edcf
	https://git.kernel.org/stable/c/653d7ddf6cba867777a3d14c4f83ace008c5ad13