This is a note to let you know that I've just added the patch titled
powerpc/rtas: Prevent Spectre v1 gadget construction in sys_rtas()
to the 6.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-rtas-prevent-spectre-v1-gadget-construction-.patch
and it can be found in the queue-6.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit d61cfd990a36ab6a9e55d8c433c891b73cdd179a
Author: Nathan Lynch <nathanl@xxxxxxxxxxxxx>
Date: Thu May 30 19:44:12 2024 -0500
powerpc/rtas: Prevent Spectre v1 gadget construction in sys_rtas()
[ 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: Sasha Levin <sashal@xxxxxxxxxx>
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)
