3.16.66-rc1 review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
commit 4179cb5a4c924cd233eaadd081882425bc98f44e upstream.
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 ce6502a8f957 ("vxlan: fix a use after free in vxlan_encap_bypass"), since the dev->stats.rx_dropped change was done on the wrong device.
Fixes: d342894c5d2f ("vxlan: virtual extensible lan") Fixes: ce6502a8f957 ("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 [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/net/vxlan.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
--- a/drivers/net/vxlan.c +++ b/drivers/net/vxlan.c @@ -1772,7 +1772,7 @@ static void vxlan_encap_bypass(struct sk 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); @@ -1792,8 +1792,15 @@ static void vxlan_encap_bypass(struct sk #endif }
+ rcu_read_lock(); + dev = skb->dev; + if (unlikely(!(dev->flags & IFF_UP))) { + kfree_skb(skb); + goto drop; + } + if (dst_vxlan->flags & VXLAN_F_LEARN) - vxlan_snoop(skb->dev, &loopback, eth_hdr(skb)->h_source); + vxlan_snoop(dev, &loopback, eth_hdr(skb)->h_source);
u64_stats_update_begin(&tx_stats->syncp); tx_stats->tx_packets++; @@ -1806,8 +1813,10 @@ static void vxlan_encap_bypass(struct sk rx_stats->rx_bytes += len; u64_stats_update_end(&rx_stats->syncp); } else { +drop: dev->stats.rx_dropped++; } + rcu_read_unlock(); }
static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,