Date:   Wed, 1 Mar 2023 15:35:13 -0500
From:   "Liam R. Howlett" <Liam.Howlett@Oracle.com>
To:     Vlastimil Babka <vbabka@suse.cz>
Cc:     kernel test robot <oliver.sang@intel.com>, oe-lkp@lists.linux.dev,
        lkp@intel.com, linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>
Subject: Re: [linus:master] [mm/mmap] 04241ffe3f:
 Kernel_panic-not_syncing:Fatal_exception
Message-ID: <20230301203513.jhyqva4dup6r7nlz@revolver>
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        Vlastimil Babka <vbabka@suse.cz>,
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        "Matthew Wilcox (Oracle)" <willy@infradead.org>
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* Vlastimil Babka <vbabka@suse.cz> [230301 14:10]:
> On 3/1/23 17:50, Liam R. Howlett wrote:
> > * kernel test robot <oliver.sang@intel.com> [230301 02:21]:
> >> 
> >> Greeting,
> >> 
> >> FYI, we noticed Kernel_panic-not_syncing:Fatal_exception due to commit (built with gcc-11):
> >> 
> >> commit: 04241ffe3f0458d54c61cf6c9d58d703efda4dd5 ("mm/mmap: introduce dup_vma_anon() helper")
> >> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> >> 
> >> [test failed on linus/master f3a2439f20d918930cc4ae8f76fe1c1afd26958f]
> >> [test failed on linux-next/master 7f7a8831520f12a3cf894b0627641fad33971221]
> > 
> > I tracked the problem down in that commit.  The fix is simple enough:
> > 
> > -----------------
> > --- a/mm/mmap.c
> > +++ b/mm/mmap.c
> > @@ -802,10 +802,13 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
> >                          * If next doesn't have anon_vma, import from vma after
> >                          * next, if the vma overlaps with it.
> >                          */
> > -                       if (remove != NULL && !next->anon_vma)
> > +                       if (remove2 != NULL && !next->anon_vma)
> 
> Oh I actually did notice that one too, but as it was only temporary within
> the series and already baked into git, thought there's no benefit in
> pointing it out. A problem for bisect obviously as was just confirmed.
> 
> > ----------------
> > 
> > However, that will not fix the problem in linux-next or linus/master
> > since this code is completely changed shortly after.
> > 
> > You need the fix from Vlastimil (Cc'ed).  After cherry-picking
> 
> > 07dc4b186203 ("mm/mremap: fix dup_anon_vma() in vma_merge() case 4") on
> 
> Which tree is that?
> The mm-hotfixes-stable commit is here:
> https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/commit/?h=mm-hotfixes-stable&id=4c6759967826b87f56c73e0f1deb7b76379ccd23

I got that git id from the build bots previous report of the failure.
It appears that it isn't in any of my trees, so it must be from
linux-next daily from some point.

> 
> > top of linus/master, I don't get this particular failure anymore.
> > 
> > I do get the "kernel BUG at mm/filemap.c:155!", so it might be masking
> > another problem. (Added Matthew to Cc)
> > 
> > I think the right thing to do is to include Vlastimil's fix.
> 
> Great, thanks.
> 
> > Thanks,
> > Liam
> > 
> > ...
> > 
>