CVE-2026-89636: smb: client: clear ce->tgthint in free_tgts()

CVE-2026-89636: smb: client: clear ce->tgthint in free_tgts()

[Greg Kroah-Hartman]

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

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

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

smb: client: clear ce->tgthint in free_tgts()

When free_tgts() frees all structures in ce->tlist, ce->tgthint
is left pointing to one of the freed cache_dfs_tgt structures.

If ce->tgthint is not reset before it is used later, it results
in a use-after-free.

Set ce->tgthint to NULL in free_tgts() after the elements are
freed to reflect that no elements remain.

The Linux kernel CVE team has assigned CVE-2026-89636 to this issue.


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

	Issue introduced in 5.0 with commit 54be1f6c1c37498bba557049df646cc239fa37e3 and fixed in 6.12.109 with commit 7507bd1885643d0461a6017767492450af1ce2a3
	Issue introduced in 5.0 with commit 54be1f6c1c37498bba557049df646cc239fa37e3 and fixed in 6.18.50 with commit 9ab46a13798a61d9d020b01d4e57efdabe6624fa
	Issue introduced in 5.0 with commit 54be1f6c1c37498bba557049df646cc239fa37e3 and fixed in 7.2.4 with commit 5baab40404a9393bcc0b7b8f1950bf2c307e0984
	Issue introduced in 5.0 with commit 54be1f6c1c37498bba557049df646cc239fa37e3 and fixed in 7.3-rc1 with commit b1b741cf8e7ce1b91d937e23decd3d3358748700

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-2026-89636
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/smb/client/dfs_cache.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/7507bd1885643d0461a6017767492450af1ce2a3
	https://git.kernel.org/stable/c/9ab46a13798a61d9d020b01d4e57efdabe6624fa
	https://git.kernel.org/stable/c/5baab40404a9393bcc0b7b8f1950bf2c307e0984
	https://git.kernel.org/stable/c/b1b741cf8e7ce1b91d937e23decd3d3358748700