ipv4: fix lockdep splat in rt_cache_seq_show

After commit f2c31e32b378 (fix NULL dereferences in check_peer_redir()),
dst_get_neighbour() should be guarded by rcu_read_lock() /
rcu_read_unlock() section.

Reported-by: Miles Lane <miles.lane@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 2 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 5c2847247f51..57e01bc60947 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -417,9 +417,13 @@ static int rt_cache_seq_show(struct seq_file *seq, void *v)
         else {
                 struct rtable *r = v;
                 struct neighbour *n;
-                int len;
+                int len, HHUptod;
 
+                rcu_read_lock();
                 n = dst_get_neighbour(&r->dst);
+                HHUptod = (n && (n->nud_state & NUD_CONNECTED)) ? 1 : 0;
+                rcu_read_unlock();
+
                 seq_printf(seq, "%s\t%08X\t%08X\t%8X\t%d\t%u\t%d\t"
                               "%08X\t%d\t%u\t%u\t%02X\t%d\t%1d\t%08X%n",
                         r->dst.dev ? r->dst.dev->name : "*",
@@ -433,7 +437,7 @@ static int rt_cache_seq_show(struct seq_file *seq, void *v)
                               dst_metric(&r->dst, RTAX_RTTVAR)),
                         r->rt_key_tos,
                         -1,
-                        (n && (n->nud_state & NUD_CONNECTED)) ? 1 : 0,
+                        HHUptod,
                         r->rt_spec_dst, &len);
 
                 seq_printf(seq, "%*s\n", 127 - len, "");