linux-kernel - Re: WARNING in ion

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Date:   Thu, 4 Jan 2018 17:45:54 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>, devel@...verdev.osuosl.org,
        syzbot <syzbot+fa2d5f63ee5904a0115a@...kaller.appspotmail.com>,
        tkjos@...roid.com, syzkaller-bugs@...glegroups.com,
        LKML <linux-kernel@...r.kernel.org>, arve@...roid.com,
        maco@...roid.com, sumit.semwal@...aro.org
Subject: Re: WARNING in ion_ioctl

On Thu, Jan 04, 2018 at 03:13:01PM +0100, 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.


With pr_warn() you have to impliment the _ONCE() logic yourself which
is sort of a pain.

regards,
dan carpenter