[PATCH net] ipv4: prevent potential spectre v1 gadget in fib_metrics_match()

[Eric Dumazet <edumazet@google.com>]

    if (!type)
        continue;
    if (type > RTAX_MAX)
        return false;
    ...
    fi_val = fi->fib_metrics->metrics[type - 1];

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

Fixes: 5f9ae3d9e7e4 ("ipv4: do metrics match when looking up and deleting a route")
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/fib_semantics.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index ce9ff3c62e84055393ca1ff98f1d2ae391978638..3bb890a40ed73626acba8c22044d1c5f99c872e8 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -30,6 +30,7 @@
 #include <linux/slab.h>
 #include <linux/netlink.h>
 #include <linux/hash.h>
+#include <linux/nospec.h>
 
 #include <net/arp.h>
 #include <net/inet_dscp.h>
@@ -1022,6 +1023,7 @@ bool fib_metrics_match(struct fib_config *cfg, struct fib_info *fi)
 		if (type > RTAX_MAX)
 			return false;
 
+		type = array_index_nospec(type, RTAX_MAX + 1);
 		if (type == RTAX_CC_ALGO) {
 			char tmp[TCP_CA_NAME_MAX];
 			bool ecn_ca = false;
-- 
2.39.1.405.gd4c25cc71f-goog