Subject: CVE-2024-46774: powerpc/rtas: Prevent Spectre v1 gadget construction in sys_rtas()

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

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

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

powerpc/rtas: Prevent Spectre v1 gadget construction in sys_rtas()

Smatch warns:

  arch/powerpc/kernel/rtas.c:1932 __do_sys_rtas() warn: potential
  spectre issue 'args.args' [r] (local cap)

The 'nargs' and 'nret' locals come directly from a user-supplied
buffer and are used as indexes into a small stack-based array and as
inputs to copy_to_user() after they are subject to bounds checks.

Use array_index_nospec() after the bounds checks to clamp these values
for speculative execution.

The Linux kernel CVE team has assigned CVE-2024-46774 to this issue.

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

	Fixed in 6.10.10 with commit 68d815648094
	Fixed in 6.11 with commit 0974d03eb479

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-2024-46774
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/powerpc/kernel/rtas.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/68d8156480940b79227d58865ec5d2947b9384a8
	https://git.kernel.org/stable/c/0974d03eb479384466d828d65637814bee6b26d7