[PATCH] isdn/gigaset: check endpoint null in gigaset_probe

[PATCH] isdn/gigaset: check endpoint null in gigaset_probe

[Phong Tran]

This fixed the potential reference NULL pointer while using variable
endpoint.

Reported-by: syzbot+35b1c403a14f5c89eba7@syzkaller.appspotmail.com
Tested by syzbot:
https://groups.google.com/d/msg/syzkaller-bugs/wnHG8eRNWEA/Qn2HhjNdBgAJ

Signed-off-by: Phong Tran <tranmanphong@gmail.com>
---
 drivers/isdn/gigaset/usb-gigaset.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/isdn/gigaset/usb-gigaset.c b/drivers/isdn/gigaset/usb-gigaset.c
index 1b9b43659bdf..2e011f3db59e 100644
--- a/drivers/isdn/gigaset/usb-gigaset.c
+++ b/drivers/isdn/gigaset/usb-gigaset.c
@@ -703,6 +703,10 @@ static int gigaset_probe(struct usb_interface *interface,
 	usb_set_intfdata(interface, cs);
 
 	endpoint = &hostif->endpoint[0].desc;
+        if (!endpoint) {
+		dev_err(cs->dev, "Couldn't get control endpoint\n");
+		return -ENODEV;
+	}
 
 	buffer_size = le16_to_cpu(endpoint->wMaxPacketSize);
 	ucs->bulk_out_size = buffer_size;
@@ -722,6 +726,11 @@ static int gigaset_probe(struct usb_interface *interface,
 	}
 
 	endpoint = &hostif->endpoint[1].desc;
+        if (!endpoint) {
+		dev_err(cs->dev, "Endpoint not available\n");
+		retval = -ENODEV;
+		goto error;
+	}
 
 	ucs->busy = 0;
 
-- 
2.20.1

Re: [PATCH] isdn/gigaset: check endpoint null in gigaset_probe

[Paul Bolle]

Phong Tran schreef op vr 26-07-2019 om 20:35 [+0700]:
> This fixed the potential reference NULL pointer while using variable
> endpoint.
> 
> Reported-by: syzbot+35b1c403a14f5c89eba7@syzkaller.appspotmail.com
> Tested by syzbot:
> https://groups.google.com/d/msg/syzkaller-bugs/wnHG8eRNWEA/Qn2HhjNdBgAJ
> 
> Signed-off-by: Phong Tran <tranmanphong@gmail.com>
> ---
>  drivers/isdn/gigaset/usb-gigaset.c | 9 +++++++++

This is now drivers/staging/isdn/gigaset/usb-gigaset.c.

>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/isdn/gigaset/usb-gigaset.c b/drivers/isdn/gigaset/usb-gigaset.c
> index 1b9b43659bdf..2e011f3db59e 100644
> --- a/drivers/isdn/gigaset/usb-gigaset.c
> +++ b/drivers/isdn/gigaset/usb-gigaset.c
> @@ -703,6 +703,10 @@ static int gigaset_probe(struct usb_interface *interface,
>  	usb_set_intfdata(interface, cs);
>  
>  	endpoint = &hostif->endpoint[0].desc;
> +        if (!endpoint) {
> +		dev_err(cs->dev, "Couldn't get control endpoint\n");
> +		return -ENODEV;
> +	}

When can this happen? Is this one of those bugs that one can only trigger with
a specially crafted (evil) usb device?

>  	buffer_size = le16_to_cpu(endpoint->wMaxPacketSize);
>  	ucs->bulk_out_size = buffer_size;
> @@ -722,6 +726,11 @@ static int gigaset_probe(struct usb_interface *interface,
>  	}
>  
>  	endpoint = &hostif->endpoint[1].desc;
> +        if (!endpoint) {
> +		dev_err(cs->dev, "Endpoint not available\n");
> +		retval = -ENODEV;
> +		goto error;
> +	}
>  
>  	ucs->busy = 0;
>  

Please note that I'm very close to getting cut off from the ISDN network, so
the chances of being able to testi this on a live system are getting small. 

Thanks,


Paul Bolle

Re: [PATCH] isdn/gigaset: check endpoint null in gigaset_probe

[Phong Tran]

On 7/26/19 9:22 PM, Paul Bolle wrote:
> Phong Tran schreef op vr 26-07-2019 om 20:35 [+0700]:
>> This fixed the potential reference NULL pointer while using variable
>> endpoint.
>>
>> Reported-by: syzbot+35b1c403a14f5c89eba7@syzkaller.appspotmail.com
>> Tested by syzbot:
>> https://groups.google.com/d/msg/syzkaller-bugs/wnHG8eRNWEA/Qn2HhjNdBgAJ
>>
>> Signed-off-by: Phong Tran <tranmanphong@gmail.com>
>> ---
>>   drivers/isdn/gigaset/usb-gigaset.c | 9 +++++++++
> 
> This is now drivers/staging/isdn/gigaset/usb-gigaset.c.

this patch was created base on branch 
kasan/usb-fuzzer-usb-testing-2019.07.11 [1]
I did not notice about the driver was moved to staging.

> 
>>   1 file changed, 9 insertions(+)
>>
>> diff --git a/drivers/isdn/gigaset/usb-gigaset.c b/drivers/isdn/gigaset/usb-gigaset.c
>> index 1b9b43659bdf..2e011f3db59e 100644
>> --- a/drivers/isdn/gigaset/usb-gigaset.c
>> +++ b/drivers/isdn/gigaset/usb-gigaset.c
>> @@ -703,6 +703,10 @@ static int gigaset_probe(struct usb_interface *interface,
>>   	usb_set_intfdata(interface, cs);
>>   
>>   	endpoint = &hostif->endpoint[0].desc;
>> +        if (!endpoint) {
>> +		dev_err(cs->dev, "Couldn't get control endpoint\n");
>> +		return -ENODEV;
>> +	}
> 
> When can this happen? Is this one of those bugs that one can only trigger with
> a specially crafted (evil) usb device?
> 

Yes, in my understanding, this only happens with random test of syzbot.

>>   	buffer_size = le16_to_cpu(endpoint->wMaxPacketSize);
>>   	ucs->bulk_out_size = buffer_size;
>> @@ -722,6 +726,11 @@ static int gigaset_probe(struct usb_interface *interface,
>>   	}
>>   
>>   	endpoint = &hostif->endpoint[1].desc;
>> +        if (!endpoint) {
>> +		dev_err(cs->dev, "Endpoint not available\n");
>> +		retval = -ENODEV;
>> +		goto error;
>> +	}
>>   
>>   	ucs->busy = 0;
>>   
> 
> Please note that I'm very close to getting cut off from the ISDN network, so
> the chances of being able to testi this on a live system are getting small.
> 

This bug can be invalid now. Do you agree?
There is an instruction to report invalid bug to syzbot [2].

> Thanks,
> 
> 
> Paul Bolle
> 


[1] 
https://github.com/google/kasan/commits/usb-fuzzer-usb-testing-2019.07.11
[2] 
https://github.com/google/syzkaller/blob/master/docs/syzbot.md#communication-with-syzbot

Thanks,
Phong

Re: [PATCH] isdn/gigaset: check endpoint null in gigaset_probe

[Paul Bolle]

Hi Phong,

Phong Tran schreef op za 27-07-2019 om 08:56 [+0700]:
> On 7/26/19 9:22 PM, Paul Bolle wrote:
> > Phong Tran schreef op vr 26-07-2019 om 20:35 [+0700]:
> > > diff --git a/drivers/isdn/gigaset/usb-gigaset.c b/drivers/isdn/gigaset/usb-gigaset.c
> > > index 1b9b43659bdf..2e011f3db59e 100644
> > > --- a/drivers/isdn/gigaset/usb-gigaset.c
> > > +++ b/drivers/isdn/gigaset/usb-gigaset.c
> > > @@ -703,6 +703,10 @@ static int gigaset_probe(struct usb_interface *interface,
> > >   	usb_set_intfdata(interface, cs);
> > >   
> > >   	endpoint = &hostif->endpoint[0].desc;
> > > +        if (!endpoint) {
> > > +		dev_err(cs->dev, "Couldn't get control endpoint\n");
> > > +		return -ENODEV;
> > > +	}
> > 
> > When can this happen? Is this one of those bugs that one can only trigger with
> > a specially crafted (evil) usb device?
> > 
> 
> Yes, in my understanding, this only happens with random test of syzbot.

Looking at this again, I note the code is taking the address of a struct
usb_endpoint_descriptor that's stored somewhere in memory. That address can't
be NULL, can it?

So I haven't even looked at the fuzzer's report here, but I don't see how this
patch could help. It only adds dead code. Am I missing something and should I
drink even more coffee this Saturday morning?

> > >   	buffer_size = le16_to_cpu(endpoint->wMaxPacketSize);
> > >   	ucs->bulk_out_size = buffer_size;
> > > @@ -722,6 +726,11 @@ static int gigaset_probe(struct usb_interface *interface,
> > > 
> > Please note that I'm very close to getting cut off from the ISDN network, so
> > the chances of being able to testi this on a live system are getting small.
> > 
> 
> This bug can be invalid now. Do you agree?

It's just that your patch arrived while I was busy doing my last ever test of
the gigaset driver. So please don't expect me to put much time in this report
(see 
https://lwn.net/ml/linux-kernel/20190726220541.28783-1-pebolle%40tiscali.nl/
).

Thanks,


Paul Bolle