From d2834ff1d9641a8695a09ea79cd901c7b6d4d05f Mon Sep 17 00:00:00 2001 From: Nathan Lynch Date: Thu, 30 May 2024 19:44:12 -0500 Subject: [PATCH] powerpc/rtas: Prevent Spectre v1 gadget construction in sys_rtas() commit 0974d03eb479384466d828d65637814bee6b26d7 upstream. 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 Reported-by: Breno Leitao Reviewed-by: Breno Leitao Signed-off-by: Michael Ellerman Link: https://msgid.link/20240530-sys_rtas-nargs-nret-v1-1-129acddd4d89@linux.ibm.com [Minor context change fixed] Signed-off-by: Cliff Liu Signed-off-by: He Zhe Signed-off-by: Greg Kroah-Hartman --- 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 5976a25c6264d..a8299981798a8 100644 --- a/arch/powerpc/kernel/rtas.c +++ b/arch/powerpc/kernel/rtas.c @@ -16,6 +16,7 @@ #include #include #include +#include #include #include #include @@ -1173,6 +1174,9 @@ 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) -- 2.47.3