Re: [PATCH-for-6.0] net: tap: fix crash on hotplug

[Peter Maydell <peter.maydell@linaro.org>]

On Wed, 21 Apr 2021 at 16:24, Cole Robinson <crobinso@redhat.com> wrote:
>
> Attempting to hotplug a tap nic with libvirt will crash qemu:
>
> $ sudo virsh attach-interface f32 network default
> error: Failed to attach interface
> error: Unable to read from monitor: Connection reset by peer
>
> 0x000055875b7f3a99 in tap_send (opaque=0x55875e39eae0) at ../net/tap.c:206
> 206             if (!s->nc.peer->do_not_pad) {
> gdb$ bt
>
> s->nc.peer may not be set at this point. This seems to be an
> expected case, as qemu_send_packet_* explicitly checks for NULL
> s->nc.peer later.
>
> Fix it by checking for s->nc.peer here too. Padding is applied if
> s->nc.peer is not set.
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1949786
> Fixes: 969e50b61a2

Is this a regression since 5.2 ? (I guess so given the Fixes tag.)

Also, I'm kind of irritated that this was reported to RH on the
15th and we only get a patch now after rc4. I really really don't
want to have to roll an rc5, so this now has a much higher
hill to climb to get into 6.0 than if it had been reported
(eg on the "Planning" wiki page) as a for-6.0 issue before rc4
was tagged...

thanks
-- PMM