ipv4: Fix a data-race around sysctl_fib_multipath_use_neigh.

While reading sysctl_fib_multipath_use_neigh, it can be changed
concurrently.  Thus, we need to add READ_ONCE() to its reader.

Fixes: a6db4494d218 ("net: ipv4: Consider failed nexthops in multipath routes")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index d9fdcba..db7b250 100644 (file)
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -2216,7 +2216,7 @@ void fib_select_multipath(struct fib_result *res, int hash)
        }
 
        change_nexthops(fi) {
-               if (net->ipv4.sysctl_fib_multipath_use_neigh) {
+               if (READ_ONCE(net->ipv4.sysctl_fib_multipath_use_neigh)) {
                        if (!fib_good_nh(nexthop_nh))
                                continue;
                        if (!first) {