[PATCH net] vxlan: Fix GRO cells race condition between receive and link delete

[PATCH net] vxlan: Fix GRO cells race condition between receive and link delete

[Stefano Brivio]

If we receive a packet while deleting a VXLAN device, there's a chance
vxlan_rcv() is called at the same time as vxlan_dellink(). This is fine,
except that vxlan_dellink() should never ever touch stuff that's still in
use, such as the GRO cells list.

Otherwise, vxlan_rcv() crashes while queueing packets via
gro_cells_receive().

Move the gro_cells_destroy() to vxlan_uninit(), which runs after the RCU
grace period is elapsed and nothing needs the gro_cells anymore.

This is now done in the same way as commit 8e816df87997 ("geneve: Use GRO
cells infrastructure.") originally implemented for GENEVE.

Reported-by: Jianlin Shi <jishi@redhat.com>
Fixes: 58ce31cca1ff ("vxlan: GRO support at tunnel layer")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
---
 drivers/net/vxlan.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index a3c46d78d216..76abd31e8d56 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -2767,6 +2767,8 @@ static void vxlan_uninit(struct net_device *dev)
 {
 	struct vxlan_dev *vxlan = netdev_priv(dev);
 
+	gro_cells_destroy(&vxlan->gro_cells);
+
 	vxlan_fdb_delete_default(vxlan, vxlan->cfg.vni);
 
 	free_percpu(dev->tstats);
@@ -3942,7 +3944,6 @@ static void vxlan_dellink(struct net_device *dev, struct list_head *head)
 
 	vxlan_flush(vxlan, true);
 
-	gro_cells_destroy(&vxlan->gro_cells);
 	list_del(&vxlan->next);
 	unregister_netdevice_queue(dev, head);
 }
-- 
2.20.1

Re: [PATCH net] vxlan: Fix GRO cells race condition between receive and link delete

[Eric Dumazet]

On 03/08/2019 07:40 AM, Stefano Brivio wrote:
> If we receive a packet while deleting a VXLAN device, there's a chance
> vxlan_rcv() is called at the same time as vxlan_dellink(). This is fine,
> except that vxlan_dellink() should never ever touch stuff that's still in
> use, such as the GRO cells list.
> 
> Otherwise, vxlan_rcv() crashes while queueing packets via
> gro_cells_receive().
> 
> Move the gro_cells_destroy() to vxlan_uninit(), which runs after the RCU
> grace period is elapsed and nothing needs the gro_cells anymore.
> 
> This is now done in the same way as commit 8e816df87997 ("geneve: Use GRO
> cells infrastructure.") originally implemented for GENEVE.
> 
> Reported-by: Jianlin Shi <jishi@redhat.com>
> Fixes: 58ce31cca1ff ("vxlan: GRO support at tunnel layer")
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
> Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>

Nice catch, thanks.

Reviewed-by: Eric Dumazet <edumazet@google.com>

Re: [PATCH net] vxlan: Fix GRO cells race condition between receive and link delete

[David Miller]

From: Stefano Brivio <sbrivio@redhat.com>
Date: Fri,  8 Mar 2019 16:40:57 +0100

> If we receive a packet while deleting a VXLAN device, there's a chance
> vxlan_rcv() is called at the same time as vxlan_dellink(). This is fine,
> except that vxlan_dellink() should never ever touch stuff that's still in
> use, such as the GRO cells list.
> 
> Otherwise, vxlan_rcv() crashes while queueing packets via
> gro_cells_receive().
> 
> Move the gro_cells_destroy() to vxlan_uninit(), which runs after the RCU
> grace period is elapsed and nothing needs the gro_cells anymore.
> 
> This is now done in the same way as commit 8e816df87997 ("geneve: Use GRO
> cells infrastructure.") originally implemented for GENEVE.
> 
> Reported-by: Jianlin Shi <jishi@redhat.com>
> Fixes: 58ce31cca1ff ("vxlan: GRO support at tunnel layer")
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
> Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>

Applied and queued up for -stable, thank you.