CVE-2026-64380: smb: client: harden POSIX SID length parsing

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

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

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

smb: client: harden POSIX SID length parsing

posix_info_sid_size() reads sid[1] to obtain the subauthority count,
but its existing boundary check still accepts buffers with only one
remaining byte. Require two bytes before reading sid[1] so all client
paths that reuse the helper reject truncated POSIX SIDs safely.

The Linux kernel CVE team has assigned CVE-2026-64380 to this issue.


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

	Issue introduced in 5.7 with commit 349e13ad30b45998bb9937cfe0b32be6f951976d and fixed in 5.10.261 with commit 171605aed68380c2fa75dff9b3a1ed427c50065b
	Issue introduced in 5.7 with commit 349e13ad30b45998bb9937cfe0b32be6f951976d and fixed in 5.15.212 with commit 4213c1208978483021d7d125c131de3985d38f61
	Issue introduced in 5.7 with commit 349e13ad30b45998bb9937cfe0b32be6f951976d and fixed in 6.1.178 with commit 96e889bc1e759c83f25093e8c2f3da31b4973f30
	Issue introduced in 5.7 with commit 349e13ad30b45998bb9937cfe0b32be6f951976d and fixed in 6.6.145 with commit 0de5b8e76847f5de26f364a82c6602c4881c30da
	Issue introduced in 5.7 with commit 349e13ad30b45998bb9937cfe0b32be6f951976d and fixed in 6.12.96 with commit 427eb7eb46425fec845a43e861f3d6e2899cae59
	Issue introduced in 5.7 with commit 349e13ad30b45998bb9937cfe0b32be6f951976d and fixed in 6.18.39 with commit 86c5d470f5d42e61123b2f4b4f0b91f4eee5b980
	Issue introduced in 5.7 with commit 349e13ad30b45998bb9937cfe0b32be6f951976d and fixed in 7.1.4 with commit 46a84715a015cb48e1b9c219dc88c03d8a541ea4
	Issue introduced in 5.7 with commit 349e13ad30b45998bb9937cfe0b32be6f951976d and fixed in 7.2-rc2 with commit 7ad2bcf2441430bb2e918fb3ef9a90d775a6e422

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-2026-64380
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/smb2pdu.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/171605aed68380c2fa75dff9b3a1ed427c50065b
	https://git.kernel.org/stable/c/4213c1208978483021d7d125c131de3985d38f61
	https://git.kernel.org/stable/c/96e889bc1e759c83f25093e8c2f3da31b4973f30
	https://git.kernel.org/stable/c/0de5b8e76847f5de26f364a82c6602c4881c30da
	https://git.kernel.org/stable/c/427eb7eb46425fec845a43e861f3d6e2899cae59
	https://git.kernel.org/stable/c/86c5d470f5d42e61123b2f4b4f0b91f4eee5b980
	https://git.kernel.org/stable/c/46a84715a015cb48e1b9c219dc88c03d8a541ea4
	https://git.kernel.org/stable/c/7ad2bcf2441430bb2e918fb3ef9a90d775a6e422