Subject: [PATCH 26/33] vxlan: Don't call gro_cells_destroy() before device is unregistered

From: Zhiqiang Liu <[email-masked]>
Date: Sat, 16 Mar 2019 17:02:54 +0800

[ Upstream commit cc4807bb609230d8959fd732b0bf3bd4c2de8eac ]

Commit ad6c9986bcb62 ("vxlan: Fix GRO cells race condition between
receive and link delete") fixed a race condition for the typical case a vxlan
device is dismantled from the current netns. But if a netns is dismantled,
vxlan_destroy_tunnels() is called to schedule a unregister_netdevice_queue()
of all the vxlan tunnels that are related to this netns.

In vxlan_destroy_tunnels(), gro_cells_destroy() is called and finished before
unregister_netdevice_queue(). This means that the gro_cells_destroy() call is
done too soon, for the same reasons explained in above commit.

So we need to fully respect the RCU rules, and thus must remove the
gro_cells_destroy() call or risk use after-free.

Fixes: 58ce31cca1ff ("vxlan: GRO support at tunnel layer")
Signed-off-by: Suanming.Mou <[email-masked]>
Suggested-by: Eric Dumazet <[email-masked]>
Reviewed-by: Stefano Brivio <[email-masked]>
Reviewed-by: Zhiqiang Liu <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 drivers/net/vxlan.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index d6fb6a89f9b3..5006daed2e96 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -4184,10 +4184,8 @@ static void vxlan_destroy_tunnels(struct net *net, struct list_head *head)
 		/* If vxlan->dev is in the same netns, it has already been added
 		 * to the list by the previous loop.
 		 */
-		if (!net_eq(dev_net(vxlan->dev), net)) {
-			gro_cells_destroy(&vxlan->gro_cells);
+		if (!net_eq(dev_net(vxlan->dev), net))
 			unregister_netdevice_queue(vxlan->dev, head);
-		}
 	}
 
 	for (h = 0; h < PORT_HASH_SIZE; ++h)
-- 
2.20.1