From: Nathan Lynch <[email protected]> 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 <[email protected]> Reported-by: Breno Leitao <[email protected]> --- Based on a change originally submitted by Breno Leitao in 2018: https://lore.kernel.org/linuxppc-dev/[email protected]/ I've used a Reported-by: tag to credit Breno, let me know if you would prefer a different tag (perhaps Co-developed-by?) --- 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 8064d9c3de86..f7e86e09c49f 100644 --- a/arch/powerpc/kernel/rtas.c +++ b/arch/powerpc/kernel/rtas.c @@ -19,6 +19,7 @@ #include <linux/lockdep.h> #include <linux/memblock.h> #include <linux/mutex.h> +#include <linux/nospec.h> #include <linux/of.h> #include <linux/of_fdt.h> #include <linux/reboot.h> @@ -1916,6 +1917,9 @@ 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) --- base-commit: be2fc65d66e0406cc9d39d40becaecdf4ee765f3 change-id: 20240530-sys_rtas-nargs-nret-a188eaf5a500 Best regards, -- Nathan Lynch <[email protected]>
