Re: usb/media/em28xx: use-after-free in em28xx_dvb_fini

Re: usb/media/em28xx: use-after-free in em28xx_dvb_fini

[Gustavo A. R. Silva]

Hi Andrey,

Could you please try this patch?

Thank you

Gustavo A. R. Silva

---
 drivers/media/usb/em28xx/em28xx-dvb.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/media/usb/em28xx/em28xx-dvb.c b/drivers/media/usb/em28xx/em28xx-dvb.c
index 4a7db62..fc3fb92 100644
--- a/drivers/media/usb/em28xx/em28xx-dvb.c
+++ b/drivers/media/usb/em28xx/em28xx-dvb.c
@@ -2073,6 +2073,9 @@ static int em28xx_dvb_fini(struct em28xx *dev)
 	struct em28xx_dvb *dvb;
 	struct i2c_client *client;
 
+	if (!dev)
+		return 0;
+
 	if (dev->is_audio_only) {
 		/* Shouldn't initialize IR for this interface */
 		return 0;
-- 
2.7.4

Re: usb/media/em28xx: use-after-free in em28xx_dvb_fini

[Andrey Konovalov]

On Tue, Nov 7, 2017 at 10:18 PM, Gustavo A. R. Silva
<garsilva@embeddedor.com> wrote:
> Hi Andrey,
>
> Could you please try this patch?
>
> Thank you
>
> Gustavo A. R. Silva

Hi Gustavo,

Still see the crash with your patch.

Thanks!

>
> ---
>  drivers/media/usb/em28xx/em28xx-dvb.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/media/usb/em28xx/em28xx-dvb.c b/drivers/media/usb/em28xx/em28xx-dvb.c
> index 4a7db62..fc3fb92 100644
> --- a/drivers/media/usb/em28xx/em28xx-dvb.c
> +++ b/drivers/media/usb/em28xx/em28xx-dvb.c
> @@ -2073,6 +2073,9 @@ static int em28xx_dvb_fini(struct em28xx *dev)
>         struct em28xx_dvb *dvb;
>         struct i2c_client *client;
>
> +       if (!dev)
> +               return 0;
> +
>         if (dev->is_audio_only) {
>                 /* Shouldn't initialize IR for this interface */
>                 return 0;
> --
> 2.7.4
>

Re: usb/media/em28xx: use-after-free in em28xx_dvb_fini

[Gustavo A. R. Silva]

Quoting Andrey Konovalov <andreyknvl@google.com>:

> On Tue, Nov 7, 2017 at 10:18 PM, Gustavo A. R. Silva
> <garsilva@embeddedor.com> wrote:
>> Hi Andrey,
>>
>> Could you please try this patch?
>>
>> Thank you
>>
>> Gustavo A. R. Silva
>
> Hi Gustavo,
>
> Still see the crash with your patch.
>
> Thanks!
>

Thank you, Andrey. I will look into this further.

--
Gustavo A. R. Silva

>>
>> ---
>>  drivers/media/usb/em28xx/em28xx-dvb.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/media/usb/em28xx/em28xx-dvb.c  
>> b/drivers/media/usb/em28xx/em28xx-dvb.c
>> index 4a7db62..fc3fb92 100644
>> --- a/drivers/media/usb/em28xx/em28xx-dvb.c
>> +++ b/drivers/media/usb/em28xx/em28xx-dvb.c
>> @@ -2073,6 +2073,9 @@ static int em28xx_dvb_fini(struct em28xx *dev)
>>         struct em28xx_dvb *dvb;
>>         struct i2c_client *client;
>>
>> +       if (!dev)
>> +               return 0;
>> +
>>         if (dev->is_audio_only) {
>>                 /* Shouldn't initialize IR for this interface */
>>                 return 0;
>> --
>> 2.7.4
>>

Re: usb/media/em28xx: use-after-free in em28xx_dvb_fini

[Andrey Konovalov]

On Wed, Nov 8, 2017 at 5:03 PM, Gustavo A. R. Silva
<garsilva@embeddedor.com> wrote:
>
> Quoting Andrey Konovalov <andreyknvl@google.com>:
>
>> On Tue, Nov 7, 2017 at 10:18 PM, Gustavo A. R. Silva
>> <garsilva@embeddedor.com> wrote:
>>>
>>> Hi Andrey,
>>>
>>> Could you please try this patch?
>>>
>>> Thank you
>>>
>>> Gustavo A. R. Silva
>>
>>
>> Hi Gustavo,
>>
>> Still see the crash with your patch.
>>
>> Thanks!
>>
>
> Thank you, Andrey. I will look into this further.

Since I'm able to reproduce this, I can apply a patch with debug
printk's or something similar and run the reproducer. Send me a patch
if you think it might help.

>
> --
> Gustavo A. R. Silva
>
>
>>>
>>> ---
>>>  drivers/media/usb/em28xx/em28xx-dvb.c | 3 +++
>>>  1 file changed, 3 insertions(+)
>>>
>>> diff --git a/drivers/media/usb/em28xx/em28xx-dvb.c
>>> b/drivers/media/usb/em28xx/em28xx-dvb.c
>>> index 4a7db62..fc3fb92 100644
>>> --- a/drivers/media/usb/em28xx/em28xx-dvb.c
>>> +++ b/drivers/media/usb/em28xx/em28xx-dvb.c
>>> @@ -2073,6 +2073,9 @@ static int em28xx_dvb_fini(struct em28xx *dev)
>>>         struct em28xx_dvb *dvb;
>>>         struct i2c_client *client;
>>>
>>> +       if (!dev)
>>> +               return 0;
>>> +
>>>         if (dev->is_audio_only) {
>>>                 /* Shouldn't initialize IR for this interface */
>>>                 return 0;
>>> --
>>> 2.7.4
>>>
>
>
>
>
>
>

Re: usb/media/em28xx: use-after-free in em28xx_dvb_fini

[Gustavo A. R. Silva]

Quoting Andrey Konovalov <andreyknvl@google.com>:

> On Wed, Nov 8, 2017 at 5:03 PM, Gustavo A. R. Silva
> <garsilva@embeddedor.com> wrote:
>>
>> Quoting Andrey Konovalov <andreyknvl@google.com>:
>>
>>> On Tue, Nov 7, 2017 at 10:18 PM, Gustavo A. R. Silva
>>> <garsilva@embeddedor.com> wrote:
>>>>
>>>> Hi Andrey,
>>>>
>>>> Could you please try this patch?
>>>>
>>>> Thank you
>>>>
>>>> Gustavo A. R. Silva
>>>
>>>
>>> Hi Gustavo,
>>>
>>> Still see the crash with your patch.
>>>
>>> Thanks!
>>>
>>
>> Thank you, Andrey. I will look into this further.
>
> Since I'm able to reproduce this, I can apply a patch with debug
> printk's or something similar and run the reproducer. Send me a patch
> if you think it might help.
>

Awesome.

I'm pretty sure this bug is related to other issues like this one:  
https://groups.google.com/forum/#!topic/syzkaller/FnJq_QkwCLQ

em28xx is an old driver and it might require some refactoring in order  
to fix such issues.

I appreciate your help.

Thank you
--
Gustavo A. R. Silva

>>
>>
>>>>
>>>> ---
>>>>  drivers/media/usb/em28xx/em28xx-dvb.c | 3 +++
>>>>  1 file changed, 3 insertions(+)
>>>>
>>>> diff --git a/drivers/media/usb/em28xx/em28xx-dvb.c
>>>> b/drivers/media/usb/em28xx/em28xx-dvb.c
>>>> index 4a7db62..fc3fb92 100644
>>>> --- a/drivers/media/usb/em28xx/em28xx-dvb.c
>>>> +++ b/drivers/media/usb/em28xx/em28xx-dvb.c
>>>> @@ -2073,6 +2073,9 @@ static int em28xx_dvb_fini(struct em28xx *dev)
>>>>         struct em28xx_dvb *dvb;
>>>>         struct i2c_client *client;
>>>>
>>>> +       if (!dev)
>>>> +               return 0;
>>>> +
>>>>         if (dev->is_audio_only) {
>>>>                 /* Shouldn't initialize IR for this interface */
>>>>                 return 0;
>>>> --
>>>> 2.7.4
>>>>
>>
>>
>>
>>
>>
>>