Stefano Garzarella
2023-Mar-29 07:16 UTC
[PATCH net v2] virtio/vsock: fix leaks due to missing skb owner
On Tue, Mar 28, 2023 at 04:29:09PM +0000, Bobby Eshleman wrote:>This patch sets the skb owner in the recv and send path for virtio. > >For the send path, this 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. > >For the recv path, this ensures correctness of accounting and also >correct transfer of ownership in vsock_loopback (when skbs are sent from >one socket and received by another). > >Fixes: 71dc9ec9ac7d ("virtio/vsock: replace virtio_vsock_pkt with sk_buff") >Signed-off-by: Bobby Eshleman <bobby.eshleman at bytedance.com> >Reported-by: Cong Wang <xiyou.wangcong at gmail.com> >Link: https://lore.kernel.org/all/ZCCbATwov4U+GBUv at pop-os.localdomain/ >--- >Changes in v2: >- virtio/vsock: add skb_set_owner_r to recv_pkt() >- Link to v1: https://lore.kernel.org/r/20230327-vsock-fix-leak-v1-1-3fede367105f at bytedance.com >--- > net/vmw_vsock/virtio_transport_common.c | 5 +++++ > 1 file changed, 5 insertions(+) > >diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c >index 957cdc01c8e8..900e5dca05f5 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: >@@ -1294,6 +1297,8 @@ void virtio_transport_recv_pkt(struct virtio_transport *t, > goto free_pkt; > } > >+ skb_set_owner_r(skb, sk); >+ > vsk = vsock_sk(sk); > > lock_sock(sk);Can you explain why we are using skb_set_owner_w/skb_set_owner_r? I'm a little concerned about 2 things: - skb_set_owner_r() documentation says: "Stream and sequenced protocols can't normally use this as they need to fit buffers in and play with them." - they increment sk_wmem_alloc and sk_rmem_alloc that we never used (IIRC) For the long run, I think we should manage memory better, and using socket accounting makes sense to me, but since we now have a different system (which we have been carrying around since the introduction of vsock), I think this change is a bit risky, especially as a fix. So my suggestion is to use skb_set_owner_sk_safe() for now, unless I missed something about why to use skb_set_owner_w/skb_set_owner_r. Thanks, Stefano