Re: [syzbot] [fs?] possible deadlock in ovl_create_object (2)

[Chris Roy]

#syz set subsystems: mtd


Regards,
- Chris

"But how could you live and have no story to tell?"

On Sun, 20 Sept 2026 at 21:50, Jörn Engel <joern@xxxxxxxxxxxxxxxx> wrote:
>
> Hello Miquèl
>
> On Sun, Sep 20, 2026 at 02:52:18PM +0200, Miquel Raynal wrote:
> >
> > Not saying this would be a bad move, it would be highly inconsistent
> > with the current code base. Every single allocation in the kernel is
> > checked. Such a change, without a documented and agreed upon method,
> > would lead to dozens fuzzing AIs sending patches to add the "missing"
> > check.
>
> If your argument is that such a change would be inappropriate for the
> patch in question, I totally agree with you.
>
> I would disagree with an argument of "we should do the wrong thing for
> the sake of consistency".  If indeed it is the wrong thing, we should
> stop doing it.  Then we can regain consistency by not doing the wrong
> thing anywhere.  In other words, consistency is irrelevant.  The only
> question should be whether such a change is right or wrong.
>
> There is also the practical consideration that changing the kmalloc
> interface will lead to thousands of changes throughout the kernel and
> requires a large time commitment from someone.  If nobody volunteers to
> be that someone, it might still be better to stick with the status quo
> for now.
>
>
> So making an entirely theoretical "if I were king for a day" kind of
> argument, I don't think GFP_KERNEL allocations should have to check for
> failure.  Neither should userspace callers to malloc.  An interface that
> frequently returns errors is pretty safe, as callers with broken error
> handling are quickly detected and fixes.  An interface that almost never
> returns errors is dangerous, as broken error handling in callers becomes
> common and will eventually lead to bizarre hard-to-reproduce failures.
>
> One of my roles in my last job was to fix userspace malloc and one of my
> fixes was to ensure it would never return an allocation failure.  If it
> returned, the caller received what it requested.  If that wasn't
> possible, the process would crash.  A crashing process isn't exactly
> desired, but it beats unpredictable behavior triggered by broken error
> handlers.  And dealing with a single error path costs significantly less
> cognitive effort than dealing with thousands of error handlers
> everywhere in the code base.
>
> Anyway, since I am not volunteering to spend a significant chunk of my
> time, this is just the opinion of someone that doesn't matter.  Feel
> free to reject it.
>
> Jörn
>
> --
> Why do musicians compose symphonies and poets write poems?
> They do it because life wouldn't have any meaning for them if they didn't.
> That's why I draw cartoons.  It's my life.
> -- Charles Shultz