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Date: Sun, 31 Jan 2021 13:59:14 +0300 From: Alexander Popov <alex.popov@...ux.com> To: David Miller <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Stefano Garzarella <sgarzare@...hat.com>, Jorgen Hansen <jhansen@...are.com>, Stefan Schmidt <stefan@...enfreihafen.org>, Jeff Vander Stoep <jeffv@...gle.com>, Greg KH <greg@...ah.com>, Linus Torvalds <torvalds@...uxfoundation.org>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, alex.popov@...ux.com Subject: [PATCH 1/1] vsock: fix the race conditions in multi-transport support 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. Signed-off-by: Alexander Popov <alex.popov@...ux.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; + 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
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