From: Nathan Lynch <nathanl@xxxxxxxxxxxxx> [ Upstream commit 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@xxxxxxxxxxxxx> Reported-by: Breno Leitao <leitao@xxxxxxxxxx> Reviewed-by: Breno Leitao <leitao@xxxxxxxxxx> Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Link: https://msgid.link/20240530-sys_rtas-nargs-nret-v1-1-129acddd4d89@xxxxxxxxxxxxx Signed-off-by: Haixiao Yan <haixiao.yan.cn@xxxxxxxxxxxxx> --- This commit is backporting 0974d03eb479 to the branch linux-5.15.y to solve the CVE-2024-46774. arch/powerpc/kernel/rtas.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c index d01a0ad57e38..f2378f51cbed 100644 --- a/arch/powerpc/kernel/rtas.c +++ b/arch/powerpc/kernel/rtas.c @@ -16,6 +16,7 @@ #include <linux/capability.h> #include <linux/delay.h> #include <linux/cpu.h> +#include <linux/nospec.h> #include <linux/sched.h> #include <linux/smp.h> #include <linux/completion.h> @@ -1076,6 +1077,9 @@ 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) -- 2.35.5
