udp: ipv4: do not use sk_dst_lock from softirq context (e47eb5df) · Commits · 戴 / test

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: ("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>

net/ipv4/udp.c

+4 −9

Original line number	Diff line number	Diff line
		@@ -1600,21 +1600,16 @@ static void flush_stack(struct sock **stack, unsigned int count,
		}

		/* 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;
		old = xchg(&sk->sk_rx_dst, dst);
		dst_release(old);
		}
		spin_unlock(&sk->sk_dst_lock);
		}

		/*
		* Multicasts and broadcasts go to each listener.

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