From 8cac0ce0a8853cae7dc01256f88bc9b7e53ad3ce Mon Sep 17 00:00:00 2001
From: Jeremy Cline <jcline@redhat.com>
Date: Tue, 31 Jul 2018 21:13:16 +0000
Subject: netlink: Fix spectre v1 gadget in netlink_create()

[ Upstream commit bc5b6c0b62b932626a135f516a41838c510c6eba ]

'protocol' is a user-controlled value, so sanitize it after the bounds
check to avoid using it for speculative out-of-bounds access to arrays
indexed by it.

This addresses the following accesses detected with the help of smatch:

* net/netlink/af_netlink.c:654 __netlink_create() warn: potential
  spectre issue 'nlk_cb_mutex_keys' [w]

* net/netlink/af_netlink.c:654 __netlink_create() warn: potential
  spectre issue 'nlk_cb_mutex_key_strings' [w]

* net/netlink/af_netlink.c:685 netlink_create() warn: potential spectre
  issue 'nl_table' [w] (local cap)

Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Jeremy Cline <jcline@redhat.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/netlink/af_netlink.c | 2 ++
 1 file changed, 2 insertions(+)

(limited to 'net/netlink/af_netlink.c')

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 818400fddc9b..9708fff318d5 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -62,6 +62,7 @@
 #include <asm/cacheflush.h>
 #include <linux/hash.h>
 #include <linux/genetlink.h>
+#include <linux/nospec.h>
 
 #include <net/net_namespace.h>
 #include <net/sock.h>
@@ -654,6 +655,7 @@ static int netlink_create(struct net *net, struct socket *sock, int protocol,
 
 	if (protocol < 0 || protocol >= MAX_LINKS)
 		return -EPROTONOSUPPORT;
+	protocol = array_index_nospec(protocol, MAX_LINKS);
 
 	netlink_lock_table();
 #ifdef CONFIG_MODULES
-- 
cgit v1.2.3