CVE-2026-72013: riscv: Prevent NULL pointer dereference in machine_kexec_prepare()

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

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

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

riscv: Prevent NULL pointer dereference in machine_kexec_prepare()

A NULL pointer dereference issue is noticed in riscv's
machine_kexec_prepare(), where image->segment[i].buf might be NULL and
copied unchecked.

The NULL buf comes from ima_add_kexec_buffer(), where kbuf is added by
kexec_add_buffer(), but kbuf.buffer is NULL, then it is copied without
a check in machine_kexec_prepare():

  kexec_file_load
    -> kimage_file_alloc_init()
       -> kimage_file_prepare_segments()
          -> ima_add_kexec_buffer()
             -> kexec_add_buffer()
    -> machine_kexec_prepare()
       -> memcpy()

Address this by adding a check before the data copy attempt.

The Linux kernel CVE team has assigned CVE-2026-72013 to this issue.


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

	Issue introduced in 5.15.47 with commit 4211742f0f9e083188f4f0ada00d6eeeef31b7c7 and fixed in 5.15.212 with commit 606cc45e871e34b80a2f63874f069387a5b44176
	Issue introduced in 5.19 with commit b7fb4d78a6ade6026d9e5cf438c2a46ab962e032 and fixed in 6.1.178 with commit c462e15497dc40abe369b3be7a2c91ac5d1be6f9
	Issue introduced in 5.19 with commit b7fb4d78a6ade6026d9e5cf438c2a46ab962e032 and fixed in 6.6.145 with commit b5f92cc4e24a298bf390b0b189a4b888c0900161
	Issue introduced in 5.19 with commit b7fb4d78a6ade6026d9e5cf438c2a46ab962e032 and fixed in 6.12.97 with commit 6ad6954492697681ebcfc1beb0eb384406cd4b65
	Issue introduced in 5.19 with commit b7fb4d78a6ade6026d9e5cf438c2a46ab962e032 and fixed in 6.18.40 with commit eadd0c2c76aee6a738f17f251434c77db3c606c8
	Issue introduced in 5.19 with commit b7fb4d78a6ade6026d9e5cf438c2a46ab962e032 and fixed in 7.1.5 with commit d5b2752a17efc165793ae38f2c24b5ed9c04ffde
	Issue introduced in 5.19 with commit b7fb4d78a6ade6026d9e5cf438c2a46ab962e032 and fixed in 7.2-rc3 with commit 81bbcff0c053c4f5c711c31a9b72fc492bd96c3f
	Issue introduced in 5.17.15 with commit 3ca8a07f141fd8eec347a82bdfa4b94164f2bb97
	Issue introduced in 5.18.4 with commit 3ba83e46b591381e718007f55c9f831fd0cd7ee8

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-2026-72013
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:
	arch/riscv/kernel/machine_kexec.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/606cc45e871e34b80a2f63874f069387a5b44176
	https://git.kernel.org/stable/c/c462e15497dc40abe369b3be7a2c91ac5d1be6f9
	https://git.kernel.org/stable/c/b5f92cc4e24a298bf390b0b189a4b888c0900161
	https://git.kernel.org/stable/c/6ad6954492697681ebcfc1beb0eb384406cd4b65
	https://git.kernel.org/stable/c/eadd0c2c76aee6a738f17f251434c77db3c606c8
	https://git.kernel.org/stable/c/d5b2752a17efc165793ae38f2c24b5ed9c04ffde
	https://git.kernel.org/stable/c/81bbcff0c053c4f5c711c31a9b72fc492bd96c3f