linux-kernel - Re: [PATCH v1 1/6] virtio console: Harden multiport against invalid host input

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Message-ID: <87fsc6qrvx.fsf@ubik.fi.intel.com>
Date:   Thu, 19 Jan 2023 20:52:02 +0200
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     mst@...hat.com, jasowang@...hat.com,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, elena.reshetova@...el.com,
        kirill.shutemov@...ux.intel.com, Andi Kleen <ak@...ux.intel.com>,
        Amit Shah <amit@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        alexander.shishkin@...ux.intel.com
Subject: Re: [PATCH v1 1/6] virtio console: Harden multiport against invalid
 host input

Greg Kroah-Hartman <gregkh@...uxfoundation.org> writes:

> On Thu, Jan 19, 2023 at 03:57:16PM +0200, Alexander Shishkin wrote:
>> From: Andi Kleen <ak@...ux.intel.com>
>> 
>> --- a/drivers/char/virtio_console.c
>> +++ b/drivers/char/virtio_console.c
>> @@ -1843,6 +1843,9 @@ static int init_vqs(struct ports_device *portdev)
>>  	int err;
>>  
>>  	nr_ports = portdev->max_nr_ports;
>> +	if (use_multiport(portdev) && nr_ports < 1)
>> +		return -EINVAL;
>> +
>>  	nr_queues = use_multiport(portdev) ? (nr_ports + 1) * 2 : 2;
>>  
>>  	vqs = kmalloc_array(nr_queues, sizeof(struct virtqueue *), GFP_KERNEL);
>> -- 
>> 2.39.0
>> 
>
> Why did I only get a small subset of these patches?

I did what get_maintainer told me. Would you like to be CC'd on the
whole thing?

> And why is the whole thread not on lore.kernel.org?

That is a mystery, some wires got crossed between my smtp and vger. I
bounced the series to lkml just now and at least some of it seems to
have landed on lore.

> And the term "hardening" is marketing fluff.   Just say, "properly parse
> input" or something like that, as what you are doing is fixing
> assumptions about the data here, not causing anything to be more (or
> less) secure.
>
> But, this still feels wrong.  Why is this happening here, in init_vqs()
> and not in the calling function that already did a bunch of validation
> of the ports and the like?  Are those checks not enough?  if not, fix it
> there, don't spread it out all over the place...

Good point! And there happens to already be 28962ec595d70 that takes
care of exactly this case. I totally missed it.

Regards,
--
Alex