CVE-2026-89728: i3c: renesas: Fix out-of-bounds access for newdevs mask

CVE-2026-89728: i3c: renesas: Fix out-of-bounds access for newdevs mask

[Greg Kroah-Hartman]

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

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

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

i3c: renesas: Fix out-of-bounds access for newdevs mask

When software initiates DAA (Dynamic Address Assignment), the controller
reports the result via the NRSPQP (Normal Response Queue Port Register).
The data length field of the response descriptor, which is accessible
through the NRSPQP register, indicates the number of devices remaining
after DAA. Consequently, when the bus is empty, this field contains the
maximum number of devices supported by the controller (8 for the Renesas
I3C controller).

Adjust the condition that computes the newly discovered devices bitmask
to prevent an out-of-bounds when the I3C bus is empty.

The Linux kernel CVE team has assigned CVE-2026-89728 to this issue.


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

	Issue introduced in 7.0 with commit e7218986319b4e903dfb4642dcbd1087cf16aaec and fixed in 7.2.4 with commit 769f5a233efcf8587f70fb2244a202d88582c746
	Issue introduced in 7.0 with commit e7218986319b4e903dfb4642dcbd1087cf16aaec and fixed in 7.3-rc1 with commit 50dec95c9d1f1f82819bc898ef2b60fa83fd4ccd

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-2026-89728
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/i3c/master/renesas-i3c.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/769f5a233efcf8587f70fb2244a202d88582c746
	https://git.kernel.org/stable/c/50dec95c9d1f1f82819bc898ef2b60fa83fd4ccd