Re: Bug: INFO_ task hung in lock_two_nondirectories

["Darrick J. Wong" <djwong@kernel.org>]

On Tue, Jan 14, 2025 at 09:59:08AM +0100, Dmitry Vyukov wrote:
> On Mon, 13 Jan 2025 at 19:08, Darrick J. Wong <djwong@kernel.org> wrote:
> >
> > On Mon, Jan 13, 2025 at 04:19:01PM +0000, Matthew Wilcox wrote:
> > > On Mon, Jan 13, 2025 at 03:38:57PM +0100, Christian Brauner wrote:
> > > > On Sun, Jan 12, 2025 at 06:00:24PM +0800, Kun Hu wrote:
> > > > > Hello,
> > > > >
> > > > > When using our customized fuzzer tool to fuzz the latest Linux kernel, the following crash (43s)
> > > > > was triggered.
> > > >
> > > > I think we need to come to an agreement at LSFMM or somewhere else that
> > > > we will by default ingore but reports from non-syzbot fuzzers. Because
> > > > we're all wasting time on them.
> >
> > No need to wait until LSFMM, I already agree with the premise of
> > deprioritizing/ignoring piles of reports that come in all at once with
> > very little analysis, an IOCCC-esque reproducer, and no effort on the
> > part of the reporter to do *anything* about the bug.
> 
> +1
> 
> It would be good to publish it somewhere on kernel.org (Documentation/
> or people.kernel.org).
> We could include the link to our guidelines for external reporters
> (where we ask to not test old kernels, reporting dups, not including
> essential info, and other silly things):
> https://github.com/google/syzkaller/blob/master/docs/linux/reporting_kernel_bugs.mdThere

/me reads, wonders if "Do NOT mimic syzbot reports" is behind why
everyone claims they have a "custom fuzzer" and proceed to leak the
letters s, y, and z in the report. :P

> is unfortunately no way to make people read all docs on the internet
> beforehand, but at least it's handy to have a link to an existing doc
> to give to people.

<nod> Good idea, we probably ought to have a kernel document setting out
our general policies about automated bug finders and linking to the
known good ones.

BTW, if one got handed a syzbot report, is there an easy way to ask your
dashboard if it already knows about that report?

--D

> > While the Google syzbot dashboard has improved remarkably since 2018,
> > particularly in the past couple of years, thanks to the people who did
> > that!  It's nice that I can fire off patches at the bot and it'll test
> > them.  That said, I don't perceive Google management to be funding much
> > of anyone to solve the problems that their fuzzer uncovers.
> >
> > This is to say nothing of the people who are coyly running their own
> > instances of syzbot sans dashboard and expecting me to download random
> > crap from Google Drive.  Hell no, I don't do that kind of thing in 2025.
> >
> > > I think it needs to be broader than that to also include "AI generated
> > > bug reports" (while not excluding AI-translated bug reports); see
> > >
> > > https://daniel.haxx.se/blog/2024/01/02/the-i-in-llm-stands-for-intelligence/
> > >
> > > so really, any "automated bug report" system is out of bounds unless
> > > previously arranged with the developers who it's supposed to be helping.
> >
> > Agree.  That's been my stance since syzbot first emerged in 2017-18.
> >
> > > We need to write that down somewhere in Documentation/process/ so we
> > > can point misguided people at it.
> > >
> > > We should also talk about how some parts of the kernel are basically
> > > unmaintained and unused, and that automated testing should be focused
> > > on parts of the kernel that are actually used.  A report about being
> > > able to crash a stock configuration of ext4 is more useful than being
> > > able to crash an unusual configuration of ufs.
> >
> > Or maybe we should try to make fuse + iouring fast enough that we can
> > kick all these old legacy drivers out to userspace. ;)
> >
> > > Distinguishing between warnings, BUG()s and actual crashes would also
> > > be a useful thing to put in this document.
> >
> > Yes.  And also state that panic_on_warn=1 is a signal that you wanted
> > fail(over) fast mode.
> >
> > --D