2023-03-27 22:13:30

by Bobby Eshleman

Subject: [PATCH net] virtio/vsock: fix leak due to missing skb owner

This patch sets the owner for the skb when being sent from a socket and
so solves the leak caused when virtio_transport_purge_skbs() finds
skb->sk is always NULL and therefore never matches it with the current
socket. Setting the owner upon allocation fixes this.

Fixes: 71dc9ec9ac7d ("virtio/vsock: replace virtio_vsock_pkt with sk_buff")
Signed-off-by: Bobby Eshleman <[email protected]>
Reported-by: Cong Wang <[email protected]>
Link: https://lore.kernel.org/all/[email protected]/
---
net/vmw_vsock/virtio_transport_common.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 957cdc01c8e8..2a2f0c1a9fbd 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -94,6 +94,9 @@ virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *info,
info->op,
info->flags);

+ if (info->vsk)
+ skb_set_owner_w(skb, sk_vsock(info->vsk));
+
return skb;

out:

---
base-commit: e5b42483ccce50d5b957f474fd332afd4ef0c27b
change-id: 20230327-vsock-fix-leak-b1cef1582aa8

Best regards,
--
Bobby Eshleman <[email protected]>

2023-03-28 08:05:18

by Stefano Garzarella

Subject: Re: [PATCH net] virtio/vsock: fix leak due to missing skb owner

On Mon, Mar 27, 2023 at 10:01:05PM +0000, Bobby Eshleman wrote:
>This patch sets the owner for the skb when being sent from a socket and
>so solves the leak caused when virtio_transport_purge_skbs() finds
>skb->sk is always NULL and therefore never matches it with the current
>socket. Setting the owner upon allocation fixes this.
>
>Fixes: 71dc9ec9ac7d ("virtio/vsock: replace virtio_vsock_pkt with sk_buff")
>Signed-off-by: Bobby Eshleman <[email protected]>
>Reported-by: Cong Wang <[email protected]>
>Link: https://lore.kernel.org/all/[email protected]/
>---
> net/vmw_vsock/virtio_transport_common.c | 3 +++
> 1 file changed, 3 insertions(+)
>
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index 957cdc01c8e8..2a2f0c1a9fbd 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -94,6 +94,9 @@ virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *info,
> info->op,
> info->flags);
>
>+ if (info->vsk)
>+ skb_set_owner_w(skb, sk_vsock(info->vsk));
>+

Should we do the same also in virtio_transport_recv_pkt()?

The skb in that cases is allocated in drivers/vhost/vsock.c and
net/vmw_vsock/virtio_transport.c using directly
virtio_vsock_alloc_skb(), because we don't know in advance which socket
it belongs to.

Then in virtio_transport_recv_pkt() we look for the socket and queue it
up. This should also solve the problem in vsock_loopback.c where we move
skb from one socket to another.

Thanks,
Stefano

2023-03-28 16:13:57

by Bobby Eshleman

Subject: Re: [PATCH net] virtio/vsock: fix leak due to missing skb owner

On Tue, Mar 28, 2023 at 09:58:00AM +0200, Stefano Garzarella wrote:
> On Mon, Mar 27, 2023 at 10:01:05PM +0000, Bobby Eshleman wrote:
> > This patch sets the owner for the skb when being sent from a socket and
> > so solves the leak caused when virtio_transport_purge_skbs() finds
> > skb->sk is always NULL and therefore never matches it with the current
> > socket. Setting the owner upon allocation fixes this.
> >
> > Fixes: 71dc9ec9ac7d ("virtio/vsock: replace virtio_vsock_pkt with sk_buff")
> > Signed-off-by: Bobby Eshleman <[email protected]>
> > Reported-by: Cong Wang <[email protected]>
> > Link: https://lore.kernel.org/all/[email protected]/
> > ---
> > net/vmw_vsock/virtio_transport_common.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
> > index 957cdc01c8e8..2a2f0c1a9fbd 100644
> > --- a/net/vmw_vsock/virtio_transport_common.c
> > +++ b/net/vmw_vsock/virtio_transport_common.c
> > @@ -94,6 +94,9 @@ virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *info,
> > info->op,
> > info->flags);
> >
> > + if (info->vsk)
> > + skb_set_owner_w(skb, sk_vsock(info->vsk));
> > +
>
> Should we do the same also in virtio_transport_recv_pkt()?
>
> The skb in that cases is allocated in drivers/vhost/vsock.c and
> net/vmw_vsock/virtio_transport.c using directly
> virtio_vsock_alloc_skb(), because we don't know in advance which socket
> it belongs to.
>
> Then in virtio_transport_recv_pkt() we look for the socket and queue it
> up. This should also solve the problem in vsock_loopback.c where we move
> skb from one socket to another.
>

That's a great point, skb_set_owner_r() in recv_pkt() will do all of the
right accounting when called by vsock_loopback_work.

I'll add that in a v2.

Thanks,
Bobby