Commit 4179cb5a authored Feb 07, 2019 by Eric Dumazet Committed by David S. Miller Feb 11, 2019

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



netif_rx() 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.

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.

Note this patch also fixes a small issue that came
with commit ce6502a8 ("vxlan: fix a use after free
in vxlan_encap_bypass"), since the dev->stats.rx_dropped
change was done on the wrong device.

Fixes: d342894c ("vxlan: virtual extensible lan")
Fixes: ce6502a8 ("vxlan: fix a use after free in vxlan_encap_bypass")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Petr Machata <petrm@mellanox.com>
Cc: Ido Schimmel <idosch@mellanox.com>
Cc: Roopa Prabhu <roopa@cumulusnetworks.com>
Cc: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 989723b0

drivers/net/vxlan.c

+11 −3

Original line number	Diff line number	Diff line
		@@ -2219,7 +2219,7 @@ static void vxlan_encap_bypass(struct sk_buff skb, struct vxlan_dev src_vxlan,
		struct pcpu_sw_netstats tx_stats, rx_stats;
		union vxlan_addr loopback;
		union vxlan_addr *remote_ip = &dst_vxlan->default_dst.remote_ip;
		struct net_device *dev = skb->dev;
		struct net_device *dev;
		int len = skb->len;

		tx_stats = this_cpu_ptr(src_vxlan->dev->tstats);
		@@ -2239,9 +2239,15 @@ static void vxlan_encap_bypass(struct sk_buff skb, struct vxlan_dev src_vxlan,
		#endif
		}

		rcu_read_lock();
		dev = skb->dev;
		if (unlikely(!(dev->flags & IFF_UP))) {
		kfree_skb(skb);
		goto drop;
		}

		if (dst_vxlan->cfg.flags & VXLAN_F_LEARN)
		vxlan_snoop(skb->dev, &loopback, eth_hdr(skb)->h_source, 0,
		vni);
		vxlan_snoop(dev, &loopback, eth_hdr(skb)->h_source, 0, vni);

		u64_stats_update_begin(&tx_stats->syncp);
		tx_stats->tx_packets++;
		@@ -2254,8 +2260,10 @@ static void vxlan_encap_bypass(struct sk_buff skb, struct vxlan_dev src_vxlan,
		rx_stats->rx_bytes += len;
		u64_stats_update_end(&rx_stats->syncp);
		} else {
		drop:
		dev->stats.rx_dropped++;
		}
		rcu_read_unlock();
		}

		static int encap_bypass_if_local(struct sk_buff skb, struct net_device dev,

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