ipv4: prevent potential spectre v1 gadget in ip_metrics_convert()

if (!type)
		continue;
	if (type > RTAX_MAX)
		return -EINVAL;
	...
	metrics[type - 1] = val;

@type being used as an array index, we need to prevent
cpu speculation or risk leaking kernel memory content.

Fixes: 6cf9dfd3bd62 ("net: fib: move metrics parsing to a helper")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20230120133040.3623463-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv4/metrics.c b/net/ipv4/metrics.c
index 7fcfdfd..0e3ee15 100644 (file)
--- a/net/ipv4/metrics.c
+++ b/net/ipv4/metrics.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0-only
 #include <linux/netlink.h>
+#include <linux/nospec.h>
 #include <linux/rtnetlink.h>
 #include <linux/types.h>
 #include <net/ip.h>
@@ -25,6 +26,7 @@ static int ip_metrics_convert(struct net *net, struct nlattr *fc_mx,
                        return -EINVAL;
                }
 
+               type = array_index_nospec(type, RTAX_MAX + 1);
                if (type == RTAX_CC_ALGO) {
                        char tmp[TCP_CA_NAME_MAX];