Commit 59cbf56f authored Mar 10, 2019 by Eric Dumazet Committed by David S. Miller Mar 10, 2019

vxlan: test dev->flags & IFF_UP before calling gro_cells_receive()



Same reasons than the ones explained in commit 4179cb5a
("vxlan: test dev->flags & IFF_UP before calling netif_rx()")

netif_rx() or gro_cells_receive() must be called under a strict contract.

At device dismantle phase, core networking clears IFF_UP
and flush_all_backlogs() is called after rcu grace period
to make sure no incoming packet might be in a cpu backlog
and still referencing the device.

A similar protocol is used for gro_cells infrastructure, as
gro_cells_destroy() will be called only after a full rcu
grace period is observed after IFF_UP has been cleared.

Most drivers call netif_rx() from their interrupt handler,
and since the interrupts are disabled at device dismantle,
netif_rx() does not have to check dev->flags & IFF_UP

Virtual drivers do not have this guarantee, and must
therefore make the check themselves.

Otherwise we risk use-after-free and/or crashes.

Fixes: d342894c ("vxlan: virtual extensible lan")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 95d6ebd5

drivers/net/vxlan.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -1731,6 +1731,14 @@ static int vxlan_rcv(struct sock sk, struct sk_buff skb)
		goto drop;
		}

		rcu_read_lock();

		if (unlikely(!(vxlan->dev->flags & IFF_UP))) {
		rcu_read_unlock();
		atomic_long_inc(&vxlan->dev->rx_dropped);
		goto drop;
		}

		stats = this_cpu_ptr(vxlan->dev->tstats);
		u64_stats_update_begin(&stats->syncp);
		stats->rx_packets++;
		@@ -1738,6 +1746,9 @@ static int vxlan_rcv(struct sock sk, struct sk_buff skb)
		u64_stats_update_end(&stats->syncp);

		gro_cells_receive(&vxlan->gro_cells, skb);

		rcu_read_unlock();

		return 0;

		drop: