Commit f38343c0 authored Sep 24, 2024 by Bowen You

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

mainline inclusion
from mainline-v6.11-rc1
commit 0974d03eb479384466d828d65637814bee6b26d7
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IARWPW
CVE: CVE-2024-46774

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0974d03eb479384466d828d65637814bee6b26d7



--------------------------------

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.

Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Reported-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240530-sys_rtas-nargs-nret-v1-1-129acddd4d89@linux.ibm.com


Conflicts:
        arch/powerpc/kernel/rtas.c
[Some header files are not included.]
Signed-off-by: Bowen You <youbowen2@huawei.com>

parent 72228248

arch/powerpc/kernel/rtas.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -21,6 +21,7 @@
		#include <linux/completion.h>
		#include <linux/cpumask.h>
		#include <linux/memblock.h>
		#include <linux/nospec.h>
		#include <linux/slab.h>
		#include <linux/reboot.h>
		#include <linux/syscalls.h>
		@@ -1168,6 +1169,9 @@ SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs)
		\|\| nargs + nret > ARRAY_SIZE(args.args))
		return -EINVAL;

		nargs = array_index_nospec(nargs, ARRAY_SIZE(args.args));
		nret = array_index_nospec(nret, ARRAY_SIZE(args.args) - nargs);

		/* Copy in args. */
		if (copy_from_user(args.args, uargs->args,
		nargs * sizeof(rtas_arg_t)) != 0)