4.4-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit 59cbf56fcd98ba2a715b6e97c4e43f773f956393 ]
Same reasons than the ones explained in commit 4179cb5a4c92 ("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: d342894c5d2f ("vxlan: virtual extensible lan") Signed-off-by: Eric Dumazet edumazet@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/vxlan.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
--- a/drivers/net/vxlan.c +++ b/drivers/net/vxlan.c @@ -1229,6 +1229,14 @@ static void vxlan_rcv(struct vxlan_sock } }
+ 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++; @@ -1237,6 +1245,8 @@ static void vxlan_rcv(struct vxlan_sock
gro_cells_receive(&vxlan->gro_cells, skb);
+ rcu_read_unlock(); + return; drop: if (tun_dst)