Re: [akpm-mm:mm-unstable] [mm] 85ad413389: BUG:kernel_NULL_pointer_dereference,address

[Oliver Sang <oliver.sang@intel.com>]

hi, Suren,

On Mon, Dec 09, 2024 at 02:20:07PM -0800, Suren Baghdasaryan wrote:
> On Sun, Dec 8, 2024 at 8:59 PM Oliver Sang <oliver.sang@intel.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@intel.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@intel.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?

we confirmed the patch fixed the issue we reported. thanks!

Tested-by: kernel test robot <oliver.sang@intel.com>