CVE-2026-93083: firmware: arm_scmi: Unwind TX receiver mailbox setup failure

CVE-2026-93083: firmware: arm_scmi: Unwind TX receiver mailbox setup failure

[Greg Kroah-Hartman]

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

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

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

firmware: arm_scmi: Unwind TX receiver mailbox setup failure

mailbox_chan_setup() can request an additional unidirectional TX
receiver channel after successfully acquiring the primary channel. If
that second request fails, the function returns immediately and leaves
the primary channel allocated.

Unwind the primary mailbox channel before returning the error so probe
deferral or other setup failures do not leave the channel busy for later
probe attempts.

The Linux kernel CVE team has assigned CVE-2026-93083 to this issue.


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

	Issue introduced in 6.4 with commit 9f68ff79ec2cb303f360a35eef5dd8f1f0f817e1 and fixed in 6.12.110 with commit babb017cf5e4600c94c23ea87175a0380235a3ee
	Issue introduced in 6.4 with commit 9f68ff79ec2cb303f360a35eef5dd8f1f0f817e1 and fixed in 6.18.52 with commit 717b8e972a667fc1bebe63cbcf0d58e692cbb491
	Issue introduced in 6.4 with commit 9f68ff79ec2cb303f360a35eef5dd8f1f0f817e1 and fixed in 7.2.6 with commit 9958f55eace8b43713c9fc54dcf90e7cdefee413
	Issue introduced in 6.4 with commit 9f68ff79ec2cb303f360a35eef5dd8f1f0f817e1 and fixed in 7.3-rc1 with commit 6f7c06744d53dc8e047725d411d7f915d9ec35ae

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-2026-93083
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:
	drivers/firmware/arm_scmi/transports/mailbox.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/babb017cf5e4600c94c23ea87175a0380235a3ee
	https://git.kernel.org/stable/c/717b8e972a667fc1bebe63cbcf0d58e692cbb491
	https://git.kernel.org/stable/c/9958f55eace8b43713c9fc54dcf90e7cdefee413
	https://git.kernel.org/stable/c/6f7c06744d53dc8e047725d411d7f915d9ec35ae