Re: [PATCH] scsi: sd: call device_del() if device_add_disk() fails

Fabio M. De Francesco
2022-03-31T17:21:22Z

On gioved? 31 marzo 2022 18:24:16 CEST Dan Carpenter wrote:
> On Thu, Mar 31, 2022 at 06:14:27PM +0200, Fabio M. De Francesco wrote:
> > On gioved? 31 marzo 2022 15:42:10 CEST Dan Carpenter wrote:
> > > Wenchao Hao, what you're saying makes a lot of sense but it raises a lot
> > > of questions in turn.
> > >
> > > Fabio, did you test your patch?
> >
> > Yes, I did, Dan. I tested it the usual way with the "#syz test:" command.
> > Obviously I have not the hardware to test code on it.
> >
>
> Yeah. What a nightmare. You posted a link to the first test. It said
> passed but definitely introduced some use after frees but how was anyone
> supposed to know?

Maybe that a "spare-time Linux developer" like me should leave these
kinds of bug fixes to more experienced people. But we should also note
that I tried two or three different patches and _all_ of them passed
the tests.

>
> No way we would have figured this out.

I think that something should change about the way Syzbot tests patches
and about how it provides the results. The other four or five bugs that
I have fixed were based mainly to the fact that they passed the Syzbot
tests.

Perhaps I've been lucky but my patches were good and they were merged.

However, I began to trust Syzbot too much. This is not how I should
approach and try to solve bugs.

> I'm working to make Smatch
> understand device_put() better but this one is way difficult.
>
> Sorry that you went through this.

Please don't be sorry :)

Believe me when I say that I cannot explain how many things I have
learned during these days while working on this issue. I see no
problems at all but only opportunities for learning.

Thank you very much!

Fabio M. De Francesco

>
> regards,
> dan carpenter
>
>