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

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