CVE-2026-80928: smack: fix cred UAF in smack_file_send_sigiotask()

CVE-2026-80928: smack: fix cred UAF in smack_file_send_sigiotask()

[Greg Kroah-Hartman]

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

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

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

smack: fix cred UAF in smack_file_send_sigiotask()

When inspecting the credentials of another task, objective credentials
(->real_cred, accessed with __task_cred()) must always be used.

Accessing ->cred on a non-current task is forbidden unless that task is
being created or destroyed; a task is allowed to change its own ->cred
pointer with no synchronization, and changing ->cred should only affect the
current syscall.

smack_file_send_sigiotask() was accessing both sets of credentials: First
tsk->cred, then __task_cred(tsk).

Fix it, always access the objective credentials here.

I have tested that this bug can lead to a KASAN-reported UAF of struct cred
in smack_file_send_sigiotask(), and that this fix prevents the race.

The Linux kernel CVE team has assigned CVE-2026-80928 to this issue.


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

	Fixed in 6.12.109 with commit b5bcf3adfa27279da4401ab8f1e1a706601a92be
	Fixed in 6.18.50 with commit ed64aa505875a3b4defd504ee8e59e1949246a62
	Fixed in 7.2.4 with commit b791401bf389a1546a830d2b381ca60fe94c7870
	Fixed in 7.3-rc1 with commit fedc88e38ce979a720cd2de042578cb5df3dc8de

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-2026-80928
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:
	security/smack/smack_lsm.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/b5bcf3adfa27279da4401ab8f1e1a706601a92be
	https://git.kernel.org/stable/c/ed64aa505875a3b4defd504ee8e59e1949246a62
	https://git.kernel.org/stable/c/b791401bf389a1546a830d2b381ca60fe94c7870
	https://git.kernel.org/stable/c/fedc88e38ce979a720cd2de042578cb5df3dc8de