vsock: fix potential deadlock in transport->release() (3f74957f) · Commits · 戴 / test

Some transports (hyperv, virtio) acquire the sock lock during the .release() callback. In the vsock_stream_connect() we call vsock_assign_transport(); if the socket was previously assigned to another transport, the vsk->transport->release() is called, but the sock lock is already held in the vsock_stream_connect(), causing a deadlock reported by syzbot: INFO: task syz-executor280:9768 blocked for more than 143 seconds. Not tainted 5.6.0-rc1-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor280 D27912 9768 9766 0x00000000 Call Trace: context_switch kernel/sched/core.c:3386 [inline] __schedule+0x934/0x1f90 kernel/sched/core.c:4082 schedule+0xdc/0x2b0 kernel/sched/core.c:4156 __lock_sock+0x165/0x290 net/core/sock.c:2413 lock_sock_nested+0xfe/0x120 net/core/sock.c:2938 virtio_transport_release+0xc4/0xd60 net/vmw_vsock/virtio_transport_common.c:832 vsock_assign_transport+0xf3/0x3b0 net/vmw_vsock/af_vsock.c:454 vsock_stream_connect+0x2b3/0xc70 net/vmw_vsock/af_vsock.c:1288 __sys_connect_file+0x161/0x1c0 net/socket.c:1857 __sys_connect+0x174/0x1b0 net/socket.c:1874 __do_sys_connect net/socket.c:1885 [inline] __se_sys_connect net/socket.c:1882 [inline] __x64_sys_connect+0x73/0xb0 net/socket.c:1882 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe To avoid this issue, this patch remove the lock acquiring in the .release() callback of hyperv and virtio transports, and it holds the lock when we call vsk->transport->release() in the vsock core. Reported-by:

<syzbot+731710996d79d0d58fbc@syzkaller.appspotmail.com> Fixes: ("vsock: use local transport when it is loaded") Signed-off-by:

Stefano Garzarella <sgarzare@redhat.com> Reviewed-by:

Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/vmw_vsock/af_vsock.c

+12 −8

Original line number	Diff line number	Diff line
		@@ -451,6 +451,12 @@ int vsock_assign_transport(struct vsock_sock vsk, struct vsock_sock psk)
		if (vsk->transport == new_transport)
		return 0;

		/* transport->release() must be called with sock lock acquired.
		* This path can only be taken during vsock_stream_connect(),
		* where we have already held the sock lock.
		* In the other cases, this function is called on a new socket
		* which is not assigned to any transport.
		*/
		vsk->transport->release(vsk);
		vsock_deassign_transport(vsk);
		}
		@@ -753,20 +759,18 @@ static void __vsock_release(struct sock *sk, int level)
		vsk = vsock_sk(sk);
		pending = NULL; /* Compiler warning. */

		/* The release call is supposed to use lock_sock_nested()
		* rather than lock_sock(), if a sock lock should be acquired.
		*/
		if (vsk->transport)
		vsk->transport->release(vsk);
		else if (sk->sk_type == SOCK_STREAM)
		vsock_remove_sock(vsk);

		/* When "level" is SINGLE_DEPTH_NESTING, use the nested
		* version to avoid the warning "possible recursive locking
		* detected". When "level" is 0, lock_sock_nested(sk, level)
		* is the same as lock_sock(sk).
		*/
		lock_sock_nested(sk, level);

		if (vsk->transport)
		vsk->transport->release(vsk);
		else if (sk->sk_type == SOCK_STREAM)
		vsock_remove_sock(vsk);

		sock_orphan(sk);
		sk->sk_shutdown = SHUTDOWN_MASK;

net/vmw_vsock/hyperv_transport.c

+0 −3

Original line number	Diff line number	Diff line
		@@ -526,12 +526,9 @@ static bool hvs_close_lock_held(struct vsock_sock *vsk)

		static void hvs_release(struct vsock_sock *vsk)
		{
		struct sock *sk = sk_vsock(vsk);
		bool remove_sock;

		lock_sock_nested(sk, SINGLE_DEPTH_NESTING);
		remove_sock = hvs_close_lock_held(vsk);
		release_sock(sk);
		if (remove_sock)
		vsock_remove_sock(vsk);
		}

net/vmw_vsock/virtio_transport_common.c

+0 −2

Original line number	Diff line number	Diff line
		@@ -829,7 +829,6 @@ void virtio_transport_release(struct vsock_sock *vsk)
		struct sock *sk = &vsk->sk;
		bool remove_sock = true;

		lock_sock_nested(sk, SINGLE_DEPTH_NESTING);
		if (sk->sk_type == SOCK_STREAM)
		remove_sock = virtio_transport_close(vsk);

		@@ -837,7 +836,6 @@ void virtio_transport_release(struct vsock_sock *vsk)
		list_del(&pkt->list);
		virtio_transport_free_pkt(pkt);
		}
		release_sock(sk);

		if (remove_sock)
		vsock_remove_sock(vsk);

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