Hi Greg, Jiri,
I searched lore.kernel.org and it seemed like CVE-2022-1462 might not
have ever been reported to you? Here is the original email with the
syzkaller reproducer.
https://seclists.org/oss-sec/2022/q2/155
The reporter proposed a fix, but it won't work. Smatch says that some
of the callers are already holding the port->lock. For example,
sci_dma_rx_complete() will deadlock.
regards,
dan carpenter
On 02. 06. 22, 4:48, Hillf Danton wrote:
> On Wed, 1 Jun 2022 21:34:26 +0300 Dan Carpenter wrote:
>> Hi Greg, Jiri,
>>
>> I searched lore.kernel.org and it seemed like CVE-2022-1462 might not
>> have ever been reported to you? Here is the original email with the
>> syzkaller reproducer.
>>
>> https://seclists.org/oss-sec/2022/q2/155
>>
>> The reporter proposed a fix, but it won't work. Smatch says that some
>> of the callers are already holding the port->lock. For example,
>> sci_dma_rx_complete() will deadlock.
>
> Hi Dan
>
> To erase the deadlock above, we need to add another helper folding
> tty_insert_flip_string() and tty_flip_buffer_push() into one nutshell,
> with buf->tail covered by port->lock.
>
> The diff attached in effect reverts
> 71a174b39f10 ("pty: do tty_flip_buffer_push without port->lock in pty_write").
>
> Only for thoughts now.
I think this the likely the best approach. Except few points inlined below.
Another would be to split tty_flip_buffer_push() into two and call only
the first one (doing smp_store_release()) inside the lock. I tried that
already, but it looks much worse.
Another would be to add flags to tty_flip_buffer_push(). Like
ONLY_ADVANCE and ONLY_QUEUE. Call with the first under the lock, the
second outside.
Ideas, comments?
> Hillf
>
> +++ b/drivers/tty/pty.c
> @@ -116,15 +116,8 @@ static int pty_write(struct tty_struct *
> if (tty->flow.stopped)
> return 0;
>
> - if (c > 0) {
> - spin_lock_irqsave(&to->port->lock, flags);
> - /* Stuff the data into the input queue of the other end */
> - c = tty_insert_flip_string(to->port, buf, c);
> - spin_unlock_irqrestore(&to->port->lock, flags);
> - /* And shovel */
> - if (c)
> - tty_flip_buffer_push(to->port);
> - }
> + if (c > 0)
> + c = tty_flip_insert_and_push_buffer(to->port, buf, c);
> return c;
> }
>
> +++ b/drivers/tty/tty_buffer.c
> @@ -554,6 +554,26 @@ void tty_flip_buffer_push(struct tty_por
> }
> EXPORT_SYMBOL(tty_flip_buffer_push);
>
> +int tty_flip_insert_and_push_buffer(struct tty_port *port, const unsigned char *string, int cnt)
It should be _insert_string_, IMO.
> +{
> + struct tty_bufhead *buf = &port->buf;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&port->lock, flags);
> + cnt = tty_insert_flip_string(port, string, cnt);
> + if (cnt) {
> + /*
> + * Paired w/ acquire in flush_to_ldisc(); ensures flush_to_ldisc() sees
> + * buffer data.
> + */
> + smp_store_release(&buf->tail->commit, buf->tail->used);
> + }
> + spin_unlock_irqrestore(&port->lock, flags);
> + queue_work(system_unbound_wq, &buf->work);
\n here please.
> + return cnt;
> +}
> +EXPORT_SYMBOL(tty_flip_insert_and_push_buffer);
No need to export this, right?
thanks,
--
js
suse labs
On 02. 06. 22, 6:48, Jiri Slaby wrote:
> On 02. 06. 22, 4:48, Hillf Danton wrote:
>> On Wed, 1 Jun 2022 21:34:26 +0300 Dan Carpenter wrote:
>>> Hi Greg, Jiri,
>>>
>>> I searched lore.kernel.org and it seemed like CVE-2022-1462 might not
>>> have ever been reported to you? Here is the original email with the
>>> syzkaller reproducer.
>>>
>>> https://seclists.org/oss-sec/2022/q2/155
>>>
>>> The reporter proposed a fix, but it won't work. Smatch says that some
>>> of the callers are already holding the port->lock. For example,
>>> sci_dma_rx_complete() will deadlock.
>>
>> Hi Dan
>>
>> To erase the deadlock above, we need to add another helper folding
>> tty_insert_flip_string() and tty_flip_buffer_push() into one nutshell,
>> with buf->tail covered by port->lock.
>>
>> The diff attached in effect reverts
>> 71a174b39f10 ("pty: do tty_flip_buffer_push without port->lock in
>> pty_write").
>>
>> Only for thoughts now.
>
> I think this the likely the best approach. Except few points inlined below.
>
> Another would be to split tty_flip_buffer_push() into two and call only
> the first one (doing smp_store_release()) inside the lock. I tried that
> already, but it looks much worse.
>
> Another would be to add flags to tty_flip_buffer_push(). Like
> ONLY_ADVANCE and ONLY_QUEUE. Call with the first under the lock, the
> second outside.
>
> Ideas, comments?
Apparently not, so Hillf, could you resend your patch after fixing the
comments below?
Thanks.
>> Hillf
>>
>> +++ b/drivers/tty/pty.c
>> @@ -116,15 +116,8 @@ static int pty_write(struct tty_struct *
>> if (tty->flow.stopped)
>> return 0;
>> - if (c > 0) {
>> - spin_lock_irqsave(&to->port->lock, flags);
>> - /* Stuff the data into the input queue of the other end */
>> - c = tty_insert_flip_string(to->port, buf, c);
>> - spin_unlock_irqrestore(&to->port->lock, flags);
>> - /* And shovel */
>> - if (c)
>> - tty_flip_buffer_push(to->port);
>> - }
>> + if (c > 0)
>> + c = tty_flip_insert_and_push_buffer(to->port, buf, c);
>> return c;
>> }
>> +++ b/drivers/tty/tty_buffer.c
>> @@ -554,6 +554,26 @@ void tty_flip_buffer_push(struct tty_por
>> }
>> EXPORT_SYMBOL(tty_flip_buffer_push);
>> +int tty_flip_insert_and_push_buffer(struct tty_port *port, const
>> unsigned char *string, int cnt)
>
> It should be _insert_string_, IMO.
>
>> +{
>> + struct tty_bufhead *buf = &port->buf;
>> + unsigned long flags;
>> +
>> + spin_lock_irqsave(&port->lock, flags);
>> + cnt = tty_insert_flip_string(port, string, cnt);
>> + if (cnt) {
>> + /*
>> + * Paired w/ acquire in flush_to_ldisc(); ensures
>> flush_to_ldisc() sees
>> + * buffer data.
>> + */
>> + smp_store_release(&buf->tail->commit, buf->tail->used);
>> + }
>> + spin_unlock_irqrestore(&port->lock, flags);
>> + queue_work(system_unbound_wq, &buf->work);
>
> \n here please.
>
>> + return cnt;
>> +}
>> +EXPORT_SYMBOL(tty_flip_insert_and_push_buffer);
>
> No need to export this, right?
>
> thanks,
--
js
suse labs
hi,
On Wed, Jun 15, 2022 at 12:47:20PM +0200, Jiri Slaby wrote:
> On 02. 06. 22, 6:48, Jiri Slaby wrote:
> > On 02. 06. 22, 4:48, Hillf Danton wrote:
> > > On Wed, 1 Jun 2022 21:34:26 +0300 Dan Carpenter wrote:
> > > > Hi Greg, Jiri,
> > > >
> > > > I searched lore.kernel.org and it seemed like CVE-2022-1462 might not
> > > > have ever been reported to you?? Here is the original email with the
> > > > syzkaller reproducer.
> > > >
> > > > https://seclists.org/oss-sec/2022/q2/155
> > > >
> > > > The reporter proposed a fix, but it won't work.? Smatch says that some
> > > > of the callers are already holding the port->lock.? For example,
> > > > sci_dma_rx_complete() will deadlock.
> > >
> > > Hi Dan
> > >
> > > To erase the deadlock above, we need to add another helper folding
> > > tty_insert_flip_string() and tty_flip_buffer_push() into one nutshell,
> > > with buf->tail covered by port->lock.
> > >
> > > The diff attached in effect reverts
> > > 71a174b39f10 ("pty: do tty_flip_buffer_push without port->lock in
> > > pty_write").
> > >
> > > Only for thoughts now.
> >
> > I think this the likely the best approach. Except few points inlined below.
> >
> > Another would be to split tty_flip_buffer_push() into two and call only
> > the first one (doing smp_store_release()) inside the lock. I tried that
> > already, but it looks much worse.
> >
> > Another would be to add flags to tty_flip_buffer_push(). Like
> > ONLY_ADVANCE and ONLY_QUEUE. Call with the first under the lock, the
> > second outside.
> >
> > Ideas, comments?
>
> Apparently not, so Hillf, could you resend your patch after fixing the
> comments below?
Any news here? I'm not sure if I missed the followup submission but
was not able to find it.
Regards,
Salvatore