CVE-2026-68401: firmware: arm_ffa: Fix out-of-bound writes in ffa_setup_and_transmit()

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

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

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

firmware: arm_ffa: Fix out-of-bound writes in ffa_setup_and_transmit()

Sashiko (locally) reports multiple out-of-bound issues in
ffa_setup_and_transmit:
1) Writing ep_mem_access->reserved can write out of bounds for FFA
   versions < 1.2 as ffa_emad_size_get() returns 16 bytes in that case
   while reserved has an offset of 24.
   Instead of zeroing fields, memset the struct to zero first based on
   the FFA version.

2) Make sure there is enough size to write constituents.

While at it, convert the only sizeof() in the driver that uses a
type instead of variable.

The Linux kernel CVE team has assigned CVE-2026-68401 to this issue.


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

	Issue introduced in 6.4 with commit 111a833dc5cbef3d05b2a796a7e23cb7f6ff2192 and fixed in 6.18.42 with commit cf5708c9d78c98214c62b1e5d049cd527a543b8e
	Issue introduced in 6.4 with commit 111a833dc5cbef3d05b2a796a7e23cb7f6ff2192 and fixed in 7.1.6 with commit 27abdaf0c5c89b06694e4c3d8318e8d6a60c1d1b
	Issue introduced in 6.4 with commit 111a833dc5cbef3d05b2a796a7e23cb7f6ff2192 and fixed in 7.2-rc4 with commit 3383ffb7ef937317361713ffcc21921a7848511a
	Issue introduced in 5.15.114 with commit 28ebfb74fbf513e0c7cd2674d8c2400ee0220d18
	Issue introduced in 6.1.31 with commit 22157f74458106c5900dbd938eb44623c22d97a0
	Issue introduced in 6.3.5 with commit b77ec23b6df41c48e88735230e11caec56163630

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-2026-68401
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_ffa/driver.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/cf5708c9d78c98214c62b1e5d049cd527a543b8e
	https://git.kernel.org/stable/c/27abdaf0c5c89b06694e4c3d8318e8d6a60c1d1b
	https://git.kernel.org/stable/c/3383ffb7ef937317361713ffcc21921a7848511a