linux-kernel - [PATCH net v3] virtio/vsock: fix leaks due to missing skb owner

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Message-Id: <20230327-vsock-fix-leak-v3-1-292cfc257531@bytedance.com>
Date:   Wed, 29 Mar 2023 16:51:58 +0000
From:   Bobby Eshleman <bobby.eshleman@...edance.com>
To:     Stefan Hajnoczi <stefanha@...hat.com>,
        Stefano Garzarella <sgarzare@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Bobby Eshleman <bobby.eshleman@...edance.com>
Cc:     kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Cong Wang <xiyou.wangcong@...il.com>
Subject: [PATCH net v3] virtio/vsock: fix leaks due to missing skb owner

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@...edance.com>
Reported-by: Cong Wang <xiyou.wangcong@...il.com>
Link: https://lore.kernel.org/all/ZCCbATwov4U+GBUv@pop-os.localdomain/
---
Changes in v3:
- virtio/vsock: use skb_set_owner_sk_safe() instead of
  skb_set_owner_{r,w}
- virtio/vsock: reject allocating/receiving skb if sk_refcnt==0 and WARN_ONCE
- Link to v2: https://lore.kernel.org/r/20230327-vsock-fix-leak-v2-1-f6619972dee0@bytedance.com

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@bytedance.com
---
 net/vmw_vsock/virtio_transport_common.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 957cdc01c8e8..c927dc302faa 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -94,6 +94,11 @@ virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *info,
 					 info->op,
 					 info->flags);
 
+	if (info->vsk && !skb_set_owner_sk_safe(skb, sk_vsock(info->vsk))) {
+		WARN_ONCE(1, "failed to allocate skb on vsock socket with sk_refcnt == 0\n");
+		goto out;
+	}
+
 	return skb;
 
 out:
@@ -1294,6 +1299,11 @@ void virtio_transport_recv_pkt(struct virtio_transport *t,
 		goto free_pkt;
 	}
 
+	if (!skb_set_owner_sk_safe(skb, sk)) {
+		WARN_ONCE(1, "receiving vsock socket has sk_refcnt == 0\n");
+		goto free_pkt;
+	}
+
 	vsk = vsock_sk(sk);
 
 	lock_sock(sk);

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

Best regards,
-- 
Bobby Eshleman <bobby.eshleman@...edance.com>