CVE-2026-74425: afs: handle CB.InitCallBackState3 requests without a server record

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

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

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

afs: handle CB.InitCallBackState3 requests without a server record

The cache manager callback path now attaches the server record to an
incoming call through the rxrpc peer's app data.  That association is
not guaranteed to exist for every callback request, and most callback
handlers already tolerate that case.

Make CB.InitCallBackState3 follow the same pattern by checking whether a
server record was attached before using it.  If the peer is not mapped
to a server record, trace the request and ignore it, matching the
existing behaviour for other unmatched callback requests.

This keeps the callback handler consistent with the rest of the cache
manager service and avoids depending on peer state that may not be
available for a given request.

The Linux kernel CVE team has assigned CVE-2026-74425 to this issue.


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

	Issue introduced in 6.15 with commit 40e8b52fe8c8ab6920ea5f59c5469b6918cce624 and fixed in 6.18.40 with commit cc848a080f7a6848dfeef441722419fdcbfe9b8d
	Issue introduced in 6.15 with commit 40e8b52fe8c8ab6920ea5f59c5469b6918cce624 and fixed in 7.1.5 with commit 0bd5f2786a878148190b4c7c259d01313d5f2357
	Issue introduced in 6.15 with commit 40e8b52fe8c8ab6920ea5f59c5469b6918cce624 and fixed in 7.2-rc2 with commit f3cf725cd284b7912d5522babb44721bf38c8887

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-2026-74425
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:
	fs/afs/cmservice.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/42e3917cdbdc3d35e191c525687a6d5427f237fd
	https://git.kernel.org/stable/c/cc848a080f7a6848dfeef441722419fdcbfe9b8d
	https://git.kernel.org/stable/c/0bd5f2786a878148190b4c7c259d01313d5f2357
	https://git.kernel.org/stable/c/f3cf725cd284b7912d5522babb44721bf38c8887