linux-kernel - Re: [akpm-mm:mm-unstable] [mm] 85ad413389: BUG:kernel_NULL_pointer

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Message-ID: <CAJuCfpGqauvtrVVqrf8ge7ba=AB3Jk7daRDdqYzOSxpB462i0w@mail.gmail.com>
Date: Mon, 9 Dec 2024 14:20:07 -0800
From: Suren Baghdasaryan <surenb@...gle.com>
To: Oliver Sang <oliver.sang@...el.com>
Cc: oe-lkp@...ts.linux.dev, lkp@...el.com, 
	Andrew Morton <akpm@...ux-foundation.org>, Christian Brauner <brauner@...nel.org>, 
	David Hildenbrand <david@...hat.com>, David Howells <dhowells@...hat.com>, 
	Davidlohr Bueso <dave@...olabs.net>, Hillf Danton <hdanton@...a.com>, Hugh Dickins <hughd@...gle.com>, 
	Jann Horn <jannh@...gle.com>, Johannes Weiner <hannes@...xchg.org>, Jonathan Corbet <corbet@....net>, 
	"Liam R. Howlett" <Liam.Howlett@...cle.com>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
	Mateusz Guzik <mjguzik@...il.com>, Matthew Wilcox <willy@...radead.org>, 
	Mel Gorman <mgorman@...hsingularity.net>, Michal Hocko <mhocko@...e.com>, 
	Minchan Kim <minchan@...gle.com>, Oleg Nesterov <oleg@...hat.com>, 
	Pasha Tatashin <pasha.tatashin@...een.com>, "Paul E. McKenney" <paulmck@...nel.org>, 
	Peter Xu <peterx@...hat.com>, Peter Zijlstra <peterz@...radead.org>, 
	Shakeel Butt <shakeel.butt@...ux.dev>, Sourav Panda <souravpanda@...gle.com>, 
	Vlastimil Babka <vbabka@...e.cz>, Wei Yang <richard.weiyang@...il.com>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [akpm-mm:mm-unstable] [mm] 85ad413389: BUG:kernel_NULL_pointer_dereference,address

On Sun, Dec 8, 2024 at 8:59 PM Oliver Sang <oliver.sang@...el.com> wrote:
>
> hi, Suren Baghdasaryan,
>
> On Sun, Dec 08, 2024 at 06:09:05PM -0800, Suren Baghdasaryan wrote:
> > On Sun, Dec 8, 2024 at 7:26 AM kernel test robot <oliver.sang@...el.com> wrote:
> > >
> > >
> > >
> > > Hello,
> > >
> > > kernel test robot noticed "BUG:kernel_NULL_pointer_dereference,address" on:
> > >
> > > commit: 85ad413389aec04cfaaba043caa8128b76c6e491 ("mm: make vma cache SLAB_TYPESAFE_BY_RCU")
> > > https://git.kernel.org/cgit/linux/kernel/git/akpm/mm.git mm-unstable
> > >
> > > in testcase: boot
> > >
> > > config: i386-randconfig-141-20241208
> > > compiler: gcc-11
> > > test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
> > >
> > > (please refer to attached dmesg/kmsg for entire log/backtrace)
> > >
> > >
> > > +------------------------------------------------+------------+------------+
> > > |                                                | 98d5eefb97 | 85ad413389 |
> > > +------------------------------------------------+------------+------------+
> > > | BUG:kernel_NULL_pointer_dereference,address    | 0          | 12         |
> > > | Oops                                           | 0          | 12         |
> > > | EIP:lock_anon_vma_root                         | 0          | 12         |
> > > | Kernel_panic-not_syncing:Fatal_exception       | 0          | 12         |
> > > +------------------------------------------------+------------+------------+
> > >
> > >
> > > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > > the same patch/commit), kindly add following tags
> > > | Reported-by: kernel test robot <oliver.sang@...el.com>
> > > | Closes: https://lore.kernel.org/oe-lkp/202412082208.db1fb2c9-lkp@intel.com
> >
> > Thanks for the report!
> > It looks like anon_vma passed to lock_anon_vma_root() is NULL but it's
> > not obvious to me why my patch would cause that.
> >
> > Oliver, how can I reproduce this locally?
> >
>
> To reproduce:
>
>         # build kernel
>         cd linux
>         cp config-6.13.0-rc1-00162-g85ad413389ae .config
>         make -j$(nproc) HOSTCC=gcc-11 CC=gcc-11 ARCH=i386 olddefconfig prepare modules_prepare bzImage modules
>         make -j$(nproc) HOSTCC=gcc-11 CC=gcc-11 ARCH=i386 INSTALL_MOD_PATH=<mod-install-dir> modules_install
>         cd <mod-install-dir>
>         find lib/ | cpio -o -H newc --quiet | gzip > modules.cgz
>
>
>         git clone https://github.com/intel/lkp-tests.git
>         cd lkp-tests
>         bin/lkp qemu -k <bzImage> -m modules.cgz job-script # job-script is attached in this email
>
>         # if come across any failure that blocks the test,
>         # please remove ~/.lkp and /lkp dir to run from a clean state.
>
>
> config and job-script files are attached in original report.
>
> one thing we want to mention is this seems only reproducible with i386 config in
> our tests.

Thanks Oliver!
I think I found the issue and
https://lore.kernel.org/all/20241209221028.1644210-1-surenb@google.com/
should fix it. Could you please try it out?