CVE-2026-74608: smb: client: Fix use-after-free in cifs_try_adding_channels()

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

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

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

smb: client: Fix use-after-free in cifs_try_adding_channels()

cifs_try_adding_channels() takes a temporary reference to an interface
before dropping iface_lock. If cifs_ses_add_channel() fails, it drops
that reference and then increments iface->weight_fulfilled.

A concurrent interface list refresh can remove the list reference while
channel creation is in progress. In that case, the failure-path
kref_put() releases the last reference and frees iface. Updating
weight_fulfilled afterward then accesses freed memory.

Increment weight_fulfilled before dropping the temporary reference,
keeping iface alive for the final access.

The Linux kernel CVE team has assigned CVE-2026-74608 to this issue.


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

	Issue introduced in 6.1.78 with commit cbc53148cc0946b72d62a3c53870cb22ce4ec284 and fixed in 6.1.183 with commit 64d7584e62ac8cdc750455c5fdc6008fc2de4f06
	Issue introduced in 6.6.17 with commit cff97d683a083b862a8bb24309e0f4d2d928128a and fixed in 6.6.152 with commit c292d4686f717c03e5022fc4ae7c782f39a94915
	Issue introduced in 6.8 with commit 6aac002bcfd554aff6d3ebb55e1660d078d70ab0 and fixed in 6.12.104 with commit 47dfac48bce7198ad4f1a388fc8c9491f878ac3b
	Issue introduced in 6.8 with commit 6aac002bcfd554aff6d3ebb55e1660d078d70ab0 and fixed in 6.18.45 with commit 1ffacbadc14530e55b8d86f7b917524f6a0fb891
	Issue introduced in 6.8 with commit 6aac002bcfd554aff6d3ebb55e1660d078d70ab0 and fixed in 7.1.9 with commit 1305eadc6a7d78a8d0a52eee29ddd2d9e8a27805
	Issue introduced in 6.8 with commit 6aac002bcfd554aff6d3ebb55e1660d078d70ab0 and fixed in 7.2 with commit 4986410316b1ae0e63c6ce418e4eb196723626e7
	Issue introduced in 6.7.5 with commit 22a6c5b3425f327e7f4c3606a72277dce82c7d83

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-2026-74608
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/sess.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/64d7584e62ac8cdc750455c5fdc6008fc2de4f06
	https://git.kernel.org/stable/c/c292d4686f717c03e5022fc4ae7c782f39a94915
	https://git.kernel.org/stable/c/47dfac48bce7198ad4f1a388fc8c9491f878ac3b
	https://git.kernel.org/stable/c/1ffacbadc14530e55b8d86f7b917524f6a0fb891
	https://git.kernel.org/stable/c/1305eadc6a7d78a8d0a52eee29ddd2d9e8a27805
	https://git.kernel.org/stable/c/4986410316b1ae0e63c6ce418e4eb196723626e7