Re: WARNING in ion_ioctl

[Laura Abbott]

On 01/04/2018 06:13 AM, Dmitry Vyukov wrote:
> On Thu, Jan 4, 2018 at 3:06 PM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxxxxxxxx
> > > 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