Re: [PATCH v2 2/2] virtio: console: add locking around c_ovq operations

[Rusty Russell <rusty@rustcorp.com.au>]

Amit Shah <amit.shah@redhat.com> writes:
> When multiple ovq operations are being performed (lots of open/close
> operations on virtio_console fds), the __send_control_msg() function can
> get confused without locking.
>
> A simple recipe to cause badness is:
> * create a QEMU VM with two virtio-serial ports
> * in the guest, do
>   while true;do echo abc >/dev/vport0p1;done
>   while true;do echo edf >/dev/vport0p2;done
>
> In one run, this caused a panic in __send_control_msg().  In another, I
> got
>
>    virtio_console virtio0: control-o:id 0 is not a head!

Both applied to my fixes branch, with CC: stable added.

For future reference, I prefer you to put the CC: stable@kernel.org tag
in if you think it's a stable candidate.

Thanks,
Rusty.