Re: [PATCH] CIFS: Fix task struct use-after-free on reconnect

[Pavel Shilovsky <piastryyy@gmail.com>]

чт, 23 янв. 2020 г. в 09:02, Vincent Whitchurch <vincent.whitchurch@axis.com>:
>
> On Thu, Jan 23, 2020 at 05:35:16PM +0100, Steve French wrote:
> > On Thu, Jan 23, 2020, 10:17 Vincent Whitchurch <vincent.whitchurch@axis.com> wrote:
> > > This can be reliably reproduced by adding the below delay to
> > > cifs_reconnect(), running find(1) on the mount, restarting the samba
> > > server while find is running, and killing find during the delay:
> > >
> > >         spin_unlock(&GlobalMid_Lock);
> > >         mutex_unlock(&server->srv_mutex);
> > >
> > >  +      msleep(10000);
> > >  +
> > >         cifs_dbg(FYI, "%s: issuing mid callbacks\n", __func__);
> > >         list_for_each_safe(tmp, tmp2, &retry_list) {
> > >                 mid_entry = list_entry(tmp, struct mid_q_entry, qhead);
> > >
> > > Fix this by holding a reference to the task struct until the MID is
> > > freed.
> >
> > Cc:stable as well?
>
> Yes, I think this bug has been there for a while.
>
> Note that the test described above usually triggers a different crash on
> kernels earlier than v5.4 because abe57073d08c13b95a46ccf48c ("CIFS: Fix
> retry mid list corruption on reconnects") has not (yet?) been backported
> to those stable kernels.

It has been only backported to 5.3.x - available from version 5.3.10.

The patch in the thread looks good. Good catch, thanks!

Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>

--
Best regards,
Pavel Shilovsky