Re: [PATCH] powerpc/kernel: Fix potential spectre v1 in syscall
From: Christophe Leroy <hidden>
Date: 2024-03-12 08:18:51
+Nathan as this is RTAS related. Le 21/08/2018 à 20:42, Breno Leitao a écrit :
The rtas syscall reads a value from a user-provided structure and uses it to index an array, being a possible area for a potential spectre v1 attack. This is the code that exposes this problem. args.rets = &args.args[nargs]; The nargs is an user provided value, and the below code is an example where the 'nargs' value would be set to XX. struct rtas_args ra; ra.nargs = htobe32(XX); syscall(__NR_rtas, &ra);
This patch has been hanging around in patchwork since 2018 and doesn't apply anymore. Is it still relevant ? If so, can you rebase et resubmit ? Thanks Christophe
quoted hunk ↗ jump to hunk
Signed-off-by: Breno Leitao <leitao@debian.org> --- arch/powerpc/kernel/rtas.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c index 8afd146bc9c7..5ef3c863003d 100644 --- a/arch/powerpc/kernel/rtas.c +++ b/arch/powerpc/kernel/rtas.c@@ -27,6 +27,7 @@ #include <linux/slab.h> #include <linux/reboot.h> #include <linux/syscalls.h> +#include <linux/nospec.h> #include <asm/prom.h> #include <asm/rtas.h>@@ -1056,7 +1057,7 @@ SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs) struct rtas_args args; unsigned long flags; char *buff_copy, *errbuf = NULL; - int nargs, nret, token; + int index, nargs, nret, token; if (!capable(CAP_SYS_ADMIN)) return -EPERM;@@ -1084,7 +1085,8 @@ SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs) if (token == RTAS_UNKNOWN_SERVICE) return -EINVAL; - args.rets = &args.args[nargs]; + index = array_index_nospec(nargs, ARRAY_SIZE(args.args)); + args.rets = &args.args[index]; memset(args.rets, 0, nret * sizeof(rtas_arg_t)); /* Need to handle ibm,suspend_me call specially */