[PATCH 00/14] Make the user mode driver code a better citizen

[Alexei Starovoitov]

On Tue, Jun 30, 2020 at 2:55 PM Tetsuo Handa
<penguin-kernel at i-love.sakura.ne.jp> wrote:
>
> On 2020/07/01 1:48, Alexei Starovoitov wrote:
> > On Tue, Jun 30, 2020 at 03:28:49PM +0900, Tetsuo Handa wrote:
> >> On 2020/06/30 5:19, Eric W. Biederman wrote:
> >>> Tetsuo Handa <penguin-kernel at i-love.sakura.ne.jp> writes:
> >>>
> >>>> On 2020/06/29 4:44, Alexei Starovoitov wrote:
> >>>>> But all the defensive programming kinda goes against general kernel style.
> >>>>> I wouldn't do it. Especially pr_info() ?!
> >>>>> Though I don't feel strongly about it.
> >>>>
> >>>> Honestly speaking, caller should check for errors and print appropriate
> >>>> messages. info->wd.mnt->mnt_root != info->wd.dentry indicates that something
> >>>> went wrong (maybe memory corruption). But other conditions are not fatal.
> >>>> That is, I consider even pr_info() here should be unnecessary.
> >>>
> >>> They were all should never happen cases.  Which is why my patches do:
> >>> if (WARN_ON_ONCE(...))
> >>
> >> No. Fuzz testing (which uses panic_on_warn=1) will trivially hit them.
> >
> > I don't believe that's true.
> > Please show fuzzing stack trace to prove your point.
> >
>
> Please find links containing "WARNING" from https://syzkaller.appspot.com/upstream . ;-)

Is it a joke? Do you understand how syzbot works?
If so, please explain how it can invoke umd_* interface.