On 01.02.2021 11:26, Stefano Garzarella wrote:
> On Sun, Jan 31, 2021 at 01:59:14PM +0300, Alexander Popov wrote:
>> There are multiple similar bugs implicitly introduced by the
>> commit c0cfa2d8a788fcf4 ("vsock: add multi-transports support") and
>> commit 6a2c0962105ae8ce ("vsock: prevent transport modules unloading").
>>
>> The bug pattern:
>> [1] vsock_sock.transport pointer is copied to a local variable,
>> [2] lock_sock() is called,
>> [3] the local variable is used.
>> VSOCK multi-transport support introduced the race condition:
>> vsock_sock.transport value may change between [1] and [2].
>>
>> Let's copy vsock_sock.transport pointer to local variables after
>> the lock_sock() call.
>
> We can add:
>
> Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
>
>>
>> Signed-off-by: Alexander Popov <alex.po...@linux.com>
>> ---
>> net/vmw_vsock/af_vsock.c | 17 ++++++++++++-----
>> 1 file changed, 12 insertions(+), 5 deletions(-)
>>
>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>> index d10916ab4526..28edac1f9aa6 100644
>> --- a/net/vmw_vsock/af_vsock.c
>> +++ b/net/vmw_vsock/af_vsock.c
>> @@ -997,9 +997,12 @@ static __poll_t vsock_poll(struct file *file, struct
>> socket *sock,
>> mask |= EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND;
>>
>> } else if (sock->type == SOCK_STREAM) {
>> - const struct vsock_transport *transport = vsk->transport;
>> + const struct vsock_transport *transport = NULL;
>
> I think we can avoid initializing to NULL since we assign it shortly
> after.
>
>> +
>> lock_sock(sk);
>>
>> + transport = vsk->transport;
>> +
>> /* Listening sockets that have connections in their accept
>> * queue can be read.
>> */
>> @@ -1082,10 +1085,11 @@ static int vsock_dgram_sendmsg(struct socket *sock,
>> struct msghdr *msg,
>> err = 0;
>> sk = sock->sk;
>> vsk = vsock_sk(sk);
>> - transport = vsk->transport;
>>
>> lock_sock(sk);
>>
>> + transport = vsk->transport;
>> +
>> err = vsock_auto_bind(vsk);
>> if (err)
>> goto out;
>> @@ -1544,10 +1548,11 @@ static int vsock_stream_setsockopt(struct
>> socket *sock,
>> err = 0;
>> sk = sock->sk;
>> vsk = vsock_sk(sk);
>> - transport = vsk->transport;
>>
>> lock_sock(sk);
>>
>> + transport = vsk->transport;
>> +
>> switch (optname) {
>> case SO_VM_SOCKETS_BUFFER_SIZE:
>> COPY_IN(val);
>> @@ -1680,7 +1685,6 @@ static int vsock_stream_sendmsg(struct socket *sock,
>> struct msghdr *msg,
>>
>> sk = sock->sk;
>> vsk = vsock_sk(sk);
>> - transport = vsk->transport;
>> total_written = 0;
>> err = 0;
>>
>> @@ -1689,6 +1693,8 @@ static int vsock_stream_sendmsg(struct socket *sock,
>> struct msghdr *msg,
>>
>> lock_sock(sk);
>>
>> + transport = vsk->transport;
>> +
>> /* Callers should not provide a destination with stream sockets. */
>> if (msg->msg_namelen) {
>> err = sk->sk_state == TCP_ESTABLISHED ? -EISCONN : -EOPNOTSUPP;
>> @@ -1823,11 +1829,12 @@ vsock_stream_recvmsg(struct socket *sock, struct
>> msghdr *msg, size_t len,
>>
>> sk = sock->sk;
>> vsk = vsock_sk(sk);
>> - transport = vsk->transport;
>> err = 0;
>>
>> lock_sock(sk);
>>
>> + transport = vsk->transport;
>> +
>> if (!transport || sk->sk_state != TCP_ESTABLISHED) {
>> /* Recvmsg is supposed to return 0 if a peer performs an
>> * orderly shutdown. Differentiate between that case and when a
>> --
>> 2.26.2
>>
>
> Thanks for fixing this issues. With the small changes applied:
>
> Reviewed-by: Stefano Garzarella <sgarz...@redhat.com>
Hello Stefano,
Thanks for the review.
I've just sent the v2.
Best regards,
Alexander
