udp: ipv4: do not use sk_dst_lock from softirq context
Using sk_dst_lock from softirq context is not supported right now.
Instead of adding BH protection everywhere,
udp_sk_rx_dst_set() can instead use xchg(), as suggested
by David.
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Fixes: 975022310233 ("udp: ipv4: must add synchronization in udp_sk_rx_dst_set()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 62c19fd..f140048 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1600,20 +1600,15 @@
}
/* For TCP sockets, sk_rx_dst is protected by socket lock
- * For UDP, we use sk_dst_lock to guard against concurrent changes.
+ * For UDP, we use xchg() to guard against concurrent changes.
*/
static void udp_sk_rx_dst_set(struct sock *sk, struct dst_entry *dst)
{
struct dst_entry *old;
- spin_lock(&sk->sk_dst_lock);
- old = sk->sk_rx_dst;
- if (likely(old != dst)) {
- dst_hold(dst);
- sk->sk_rx_dst = dst;
- dst_release(old);
- }
- spin_unlock(&sk->sk_dst_lock);
+ dst_hold(dst);
+ old = xchg(&sk->sk_rx_dst, dst);
+ dst_release(old);
}
/*