• Stefano Garzarella's avatar
    vsock: fix potential deadlock in transport->release() · 3f74957f
    Stefano Garzarella authored
    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: 408624af ("vsock: use local transport when it is loaded")
    Signed-off-by: default avatarStefano Garzarella <sgarzare@redhat.com>
    Reviewed-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    3f74957f
af_vsock.c 53.7 KB