linux-kernel - Re: WARNING in ion

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Date:   Thu, 4 Jan 2018 15:13:01 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     syzbot <syzbot+fa2d5f63ee5904a0115a@...kaller.appspotmail.com>,
        arve@...roid.com, devel@...verdev.osuosl.org,
        Laura Abbott <labbott@...hat.com>,
        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 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.