Re: [Patch net] vsock: fix recursive ->recvmsg calls

["Michael S. Tsirkin" <mst@redhat.com>]

On Sun, Aug 11, 2024 at 07:21:53PM -0700, Cong Wang wrote:
> From: Cong Wang <cong.wang@bytedance.com>
> 
> After a vsock socket has been added to a BPF sockmap, its prot->recvmsg
> has been replaced with vsock_bpf_recvmsg(). Thus the following
> recursiion could happen:
> 
> vsock_bpf_recvmsg()
>  -> __vsock_recvmsg()
>   -> vsock_connectible_recvmsg()
>    -> prot->recvmsg()
>     -> vsock_bpf_recvmsg() again
> 
> We need to fix it by calling the original ->recvmsg() without any BPF
> sockmap logic in __vsock_recvmsg().
> 
> Fixes: 634f1a7110b4 ("vsock: support sockmap")
> Reported-by: syzbot+bdb4bd87b5e22058e2a4@syzkaller.appspotmail.com
> Tested-by: syzbot+bdb4bd87b5e22058e2a4@syzkaller.appspotmail.com
> Cc: Bobby Eshleman <bobby.eshleman@bytedance.com>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Stefano Garzarella <sgarzare@redhat.com>
> Signed-off-by: Cong Wang <cong.wang@bytedance.com>

Acked-by: Michael S. Tsirkin <mst@redhat.com>

> ---
>  include/net/af_vsock.h    |  4 ++++
>  net/vmw_vsock/af_vsock.c  | 50 +++++++++++++++++++++++----------------
>  net/vmw_vsock/vsock_bpf.c |  4 ++--
>  3 files changed, 35 insertions(+), 23 deletions(-)
> 
> diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
> index 535701efc1e5..24d970f7a4fa 100644
> --- a/include/net/af_vsock.h
> +++ b/include/net/af_vsock.h
> @@ -230,8 +230,12 @@ struct vsock_tap {
>  int vsock_add_tap(struct vsock_tap *vt);
>  int vsock_remove_tap(struct vsock_tap *vt);
>  void vsock_deliver_tap(struct sk_buff *build_skb(void *opaque), void *opaque);
> +int __vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> +				int flags);
>  int vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
>  			      int flags);
> +int __vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
> +			  size_t len, int flags);
>  int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
>  			size_t len, int flags);
>  
> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
> index 4b040285aa78..0ff9b2dd86ba 100644
> --- a/net/vmw_vsock/af_vsock.c
> +++ b/net/vmw_vsock/af_vsock.c
> @@ -1270,25 +1270,28 @@ static int vsock_dgram_connect(struct socket *sock,
>  	return err;
>  }
>  
> +int __vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
> +			  size_t len, int flags)
> +{
> +	struct sock *sk = sock->sk;
> +	struct vsock_sock *vsk = vsock_sk(sk);
> +
> +	return vsk->transport->dgram_dequeue(vsk, msg, len, flags);
> +}
> +
>  int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
>  			size_t len, int flags)
>  {
>  #ifdef CONFIG_BPF_SYSCALL
> +	struct sock *sk = sock->sk;
>  	const struct proto *prot;
> -#endif
> -	struct vsock_sock *vsk;
> -	struct sock *sk;
>  
> -	sk = sock->sk;
> -	vsk = vsock_sk(sk);
> -
> -#ifdef CONFIG_BPF_SYSCALL
>  	prot = READ_ONCE(sk->sk_prot);
>  	if (prot != &vsock_proto)
>  		return prot->recvmsg(sk, msg, len, flags, NULL);
>  #endif
>  
> -	return vsk->transport->dgram_dequeue(vsk, msg, len, flags);
> +	return __vsock_dgram_recvmsg(sock, msg, len, flags);
>  }
>  EXPORT_SYMBOL_GPL(vsock_dgram_recvmsg);
>  
> @@ -2174,15 +2177,12 @@ static int __vsock_seqpacket_recvmsg(struct sock *sk, struct msghdr *msg,
>  }
>  
>  int
> -vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> -			  int flags)
> +__vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> +			    int flags)
>  {
>  	struct sock *sk;
>  	struct vsock_sock *vsk;
>  	const struct vsock_transport *transport;
> -#ifdef CONFIG_BPF_SYSCALL
> -	const struct proto *prot;
> -#endif
>  	int err;
>  
>  	sk = sock->sk;
> @@ -2233,14 +2233,6 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
>  		goto out;
>  	}
>  
> -#ifdef CONFIG_BPF_SYSCALL
> -	prot = READ_ONCE(sk->sk_prot);
> -	if (prot != &vsock_proto) {
> -		release_sock(sk);
> -		return prot->recvmsg(sk, msg, len, flags, NULL);
> -	}
> -#endif
> -
>  	if (sk->sk_type == SOCK_STREAM)
>  		err = __vsock_stream_recvmsg(sk, msg, len, flags);
>  	else
> @@ -2250,6 +2242,22 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
>  	release_sock(sk);
>  	return err;
>  }
> +
> +int
> +vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> +			  int flags)
> +{
> +#ifdef CONFIG_BPF_SYSCALL
> +	struct sock *sk = sock->sk;
> +	const struct proto *prot;
> +
> +	prot = READ_ONCE(sk->sk_prot);
> +	if (prot != &vsock_proto)
> +		return prot->recvmsg(sk, msg, len, flags, NULL);
> +#endif
> +
> +	return __vsock_connectible_recvmsg(sock, msg, len, flags);
> +}
>  EXPORT_SYMBOL_GPL(vsock_connectible_recvmsg);
>  
>  static int vsock_set_rcvlowat(struct sock *sk, int val)
> diff --git a/net/vmw_vsock/vsock_bpf.c b/net/vmw_vsock/vsock_bpf.c
> index a3c97546ab84..c42c5cc18f32 100644
> --- a/net/vmw_vsock/vsock_bpf.c
> +++ b/net/vmw_vsock/vsock_bpf.c
> @@ -64,9 +64,9 @@ static int __vsock_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int
>  	int err;
>  
>  	if (sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET)
> -		err = vsock_connectible_recvmsg(sock, msg, len, flags);
> +		err = __vsock_connectible_recvmsg(sock, msg, len, flags);
>  	else if (sk->sk_type == SOCK_DGRAM)
> -		err = vsock_dgram_recvmsg(sock, msg, len, flags);
> +		err = __vsock_dgram_recvmsg(sock, msg, len, flags);
>  	else
>  		err = -EPROTOTYPE;
>  
> -- 
> 2.34.1