ipv4: Fix a data-race around sysctl_fib_multipath_use_neigh.

[ Upstream commit 87507bcb4f5de16bb419e9509d874f4db6c0ad0f ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 70c866308abea3d16316b3960a1b48d41af7b7f9..3824b7abecf7e34f8275bcedace7af2ac0e55b17 100644 (file)
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -2232,7 +2232,7 @@ 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) {