linux-kernel - Re: WARNING in ion

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Date:   Thu, 4 Jan 2018 11:01:06 -0800
From:   Laura Abbott <labbott@...hat.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>,
        Greg KH <gregkh@...uxfoundation.org>
Cc:     syzbot <syzbot+fa2d5f63ee5904a0115a@...kaller.appspotmail.com>,
        arve@...roid.com, devel@...verdev.osuosl.org,
        LKML <linux-kernel@...r.kernel.org>, maco@...roid.com,
        sumit.semwal@...aro.org, syzkaller-bugs@...glegroups.com,
        tkjos@...roid.com
Subject: Re: WARNING in ion_ioctl

On 01/04/2018 06:13 AM, Dmitry Vyukov wrote:
> On Thu, Jan 4, 2018 at 3:06 PM, Greg KH <gregkh@...uxfoundation.org> wrote:
>> On Thu, Jan 04, 2018 at 05:57:01AM -0800, syzbot wrote:
>>> Hello,
>>>
>>> syzkaller hit the following crash on
>>> 71ee203389f7cb1c1927eab22b95baa01405791c
>>> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
>>> compiler: gcc (GCC) 7.1.1 20170620
>>> .config is attached
>>> Raw console output is attached.
>>> C reproducer is attached
>>> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
>>> for information about syzkaller reproducers
>>>
>>>
>>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>>> Reported-by: syzbot+fa2d5f63ee5904a0115a@...kaller.appspotmail.com
>>> It will help syzbot understand when the bug is fixed. See footer for
>>> details.
>>> If you forward the report, please keep this part and the footer.
>>>
>>> audit: type=1400 audit(1514734723.062:7): avc:  denied  { map } for
>>> pid=3502 comm="syzkaller809746" path="/root/syzkaller809746698" dev="sda1"
>>> ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
>>> tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
>>> WARNING: CPU: 0 PID: 3502 at drivers/staging/android/ion/ion-ioctl.c:73
>>> ion_ioctl+0x2db/0x380 drivers/staging/android/ion/ion-ioctl.c:73
>>> Kernel panic - not syncing: panic_on_warn set ...
>>
>> This is to be expected when you pass in a crappy ion ioctl structure.
>>
>> So don't do that :)
>>
>> Yeah, it's a harsh warning, but I think the userspace developers like it
>> to ensure they got their implementation correct.
>>
>> After the warning is thrown, all keeps working just fine.
> 
> Hi Greg,
> 
> Or, don't do WARNINGs on EINVAL and do pr_warn instead, as useful but
> also enables automated kernel testing with non-tainted reports, which
> is kinda a useful property.
> 

 From past experience, pr_warn was too subtle for some developers but
I'm more interested in the fuzzing at this point so I'll see about
just switching it to a pr_warn_once.

Thanks,
Laura