linux-kernel - Re: general protection fault in mas_empty_area

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Date: Mon, 22 Apr 2024 12:34:16 -0700
From: Marius Fleischer <fleischermarius@...il.com>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, maple-tree@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, syzkaller@...glegroups.com, 
	harrisonmichaelgreen@...il.com
Subject: Re: general protection fault in mas_empty_area_rev

Hi Liam,

On Mon, 22 Apr 2024 at 11:53, Liam R. Howlett <Liam.Howlett@...cle.com> wrote:
> * Marius Fleischer <fleischermarius@...il.com> [240422 14:07]:
> > Hi Liam,
> >
> > On Mon, 22 Apr 2024 at 10:05, Liam R. Howlett <Liam.Howlett@...cle.com> wrote:
> > > * Liam R. Howlett <Liam.Howlett@...cle.com> [240422 11:25]:
> > > > * Marius Fleischer <fleischermarius@...il.com> [240422 11:11]:
> > > > > Hi Liam,
> > > > >
> > > > > Thank you so much for the response!
> > > > >
> > > > > > >
> > > > > > > Crash log:
> > > > > > >
> > > > > > > general protection fault, probably for non-canonical address
> > > > > > > 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN NOPTI
> > > > > > >
> > > > > > > KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> > > > > > >
> > > > > > > CPU: 0 PID: 79545 Comm: syz-executor.0 Not tainted 6.9.0-rc4-dirty #3
> > > > > >
> > > > > > This indicates that you built with your own patches.  Could you test an
> > > > > > unmodified 6.9.0-rc4 with your setup?
> > > > > >
> > > > >
> > > > > I'm very sorry for this oversight. I had applied the patches for another bug
> > > > > from this conversation
> > > > > (https://lore.kernel.org/all/20240404070702.2744-3-osalvador@suse.de/T/#m480f21ab850996395082d0faab7f624f45b83781)
> > > > > I will test the reproducer without these patches and get back to you!
> > > >
> > > > After testing with your config, I can see that those fixes are needed to
> > > > boot.
> > > >
> > > > I am going to try 6.9-rc5 with your configuration and see if I can
> > > > trigger the issue there.
> > > >
> > >
> > > The reproducer does not trigger for me with your configuration and
> > > reproducer.
> > >
> > > Does it still happen for you in 6.9-rc5?
> > >
> > You are right, indeed, I was not able to boot v6.9-rc4 without the fixes.
> >
> > I tested the reproducer on 6.9-rc5 (ed30a4a51bb196781c8058073ea720133a65596f)
> > and it still triggers the crash in my setup. How can I help you
> > further troubleshoot
> > this issue?
>
> Can you try the attached patch and see if that stops the crash?
>

I tested your patch against 6.9-rc5. It stops the crash.

Best,
Marius