CVE-2026-68397: net/iucv: take a reference on the socket found in afiucv_hs_rcv()

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

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

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

net/iucv: take a reference on the socket found in afiucv_hs_rcv()

afiucv_hs_rcv() looks up the destination socket under iucv_sk_list.lock,
drops the lock, and then passes the socket to the afiucv_hs_callback_*()
handlers without holding a reference. AF_IUCV sockets are not
RCU-protected and are freed synchronously by iucv_sock_kill() ->
sock_put(), so a concurrent close can free the socket in the window
between read_unlock() and the handler, which then dereferences freed
memory (for example sk->sk_data_ready() in afiucv_hs_callback_syn()).

Take a reference with sock_hold() while the socket is still on the list
and release it with sock_put() once the handler has run.

The Linux kernel CVE team has assigned CVE-2026-68397 to this issue.


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

	Issue introduced in 3.2 with commit 3881ac441f642d56503818123446f7298442236b and fixed in 6.6.148 with commit 4dc0e63abf8bc7ba8892e617c1fb8b204361e022
	Issue introduced in 3.2 with commit 3881ac441f642d56503818123446f7298442236b and fixed in 6.12.101 with commit 1801cb20a5025a787d6853e19c38db138344b4b4
	Issue introduced in 3.2 with commit 3881ac441f642d56503818123446f7298442236b and fixed in 6.18.42 with commit c75a950e77356e526672cba4584080c6c8b793b6
	Issue introduced in 3.2 with commit 3881ac441f642d56503818123446f7298442236b and fixed in 7.1.6 with commit 5595ea59cdf29182cf6a270cacc1426c57b603de
	Issue introduced in 3.2 with commit 3881ac441f642d56503818123446f7298442236b and fixed in 7.2-rc4 with commit 4fa349156043dc119721d067329714179f501749

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-2026-68397
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/iucv/af_iucv.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/4dc0e63abf8bc7ba8892e617c1fb8b204361e022
	https://git.kernel.org/stable/c/1801cb20a5025a787d6853e19c38db138344b4b4
	https://git.kernel.org/stable/c/c75a950e77356e526672cba4584080c6c8b793b6
	https://git.kernel.org/stable/c/5595ea59cdf29182cf6a270cacc1426c57b603de
	https://git.kernel.org/stable/c/4fa349156043dc119721d067329714179f501749