5.15-stable review patch. If anyone has any objections, please let me know.
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From: Nathan Lynch nathanl@linux.ibm.com
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 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.... [Minor context change fixed] Signed-off-by: Cliff Liu donghua.liu@windriver.com Signed-off-by: He Zhe Zhe.He@windriver.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/powerpc/kernel/rtas.c | 4 ++++ 1 file changed, 4 insertions(+)
--- 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 _ || 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)