2022-07-15 01:56:39

by Zheyu Ma

Subject: [BUG] media: cx88-alsa: Found a bug at the probe time

Hello,

I found a bug in the driver cx88-alsa.

When the driver fails in the function snd_cx88_create() at the probe
time, it will cause a UAF bug as follows:

[ 24.343899] Trying to free already-free IRQ 0
[ 24.344815] WARNING: CPU: 7 PID: 389 at kernel/irq/manage.c:1895
free_irq+0x3a4/0x7c0
[ 24.348448] RIP: 0010:free_irq+0x3a4/0x7c0
[ 24.356716] Call Trace:
[ 24.357124] snd_cx88_dev_free+0x71/0x100 [cx88_alsa]
[ 24.358008] release_card_device+0x7d/0x190
[ 24.358699] device_release+0x97/0x1c0
[ 24.359022] kobject_put+0x144/0x1c0
[ 24.359329] snd_card_free+0xec/0x150
[ 24.360078] cx88_audio_initdev+0x8f4/0xce0 [cx88_alsa]

Since I'm not familiar with the driver, could you please give me some
hints to fix it?

regards,

Zheyu Ma

2022-07-16 19:24:41

by Randy Dunlap

Subject: Re: [BUG] media: cx88-alsa: Found a bug at the probe time

Hi--

On 7/14/22 18:54, Zheyu Ma wrote:
> Hello,
>
> I found a bug in the driver cx88-alsa.
>
> When the driver fails in the function snd_cx88_create() at the probe
> time, it will cause a UAF bug as follows:

It's not a UAF. It's a WARN() macro with an IRQ management problem,
as shown in the next 2 lines below:
>
> [ 24.343899] Trying to free already-free IRQ 0
> [ 24.344815] WARNING: CPU: 7 PID: 389 at kernel/irq/manage.c:1895
> free_irq+0x3a4/0x7c0
> [ 24.348448] RIP: 0010:free_irq+0x3a4/0x7c0
> [ 24.356716] Call Trace:
> [ 24.357124] snd_cx88_dev_free+0x71/0x100 [cx88_alsa]
> [ 24.358008] release_card_device+0x7d/0x190
> [ 24.358699] device_release+0x97/0x1c0
> [ 24.359022] kobject_put+0x144/0x1c0
> [ 24.359329] snd_card_free+0xec/0x150
> [ 24.360078] cx88_audio_initdev+0x8f4/0xce0 [cx88_alsa]
>
> Since I'm not familiar with the driver, could you please give me some
> hints to fix it?
>
> regards,
>
> Zheyu Ma

--
~Randy

2022-07-17 00:19:21

by Zheyu Ma

Subject: Re: [BUG] media: cx88-alsa: Found a bug at the probe time

On Sun, Jul 17, 2022 at 3:03 AM Randy Dunlap <[email protected]> wrote:
>
> Hi--
>
> On 7/14/22 18:54, Zheyu Ma wrote:
> > Hello,
> >
> > I found a bug in the driver cx88-alsa.
> >
> > When the driver fails in the function snd_cx88_create() at the probe
> > time, it will cause a UAF bug as follows:
>
> It's not a UAF. It's a WARN() macro with an IRQ management problem,
> as shown in the next 2 lines below:

You are right, that is indeed just a warning :)

regards,

Zheyu Ma