* Yu Zhao <yuzhao@google.com> [220419 19:23]:
> On Tue, Apr 19, 2022 at 5:18 PM Liam Howlett <liam.howlett@oracle.com> wrote:
> >
> > * Yu Zhao <yuzhao@google.com> [220419 17:59]:
> > > On Tue, Apr 19, 2022 at 9:51 AM Liam Howlett <liam.howlett@oracle.com> wrote:
> > > >
> > > > * Yu Zhao <yuzhao@google.com> [220416 15:30]:
> > > > > On Sat, Apr 16, 2022 at 9:19 AM Liam Howlett <liam.howlett@oracle.com> wrote:
> > > > > >
> > > > >
> > > > > <snipped>
> > > > >
> > > > > > How did you hit this issue?  Just on boot?
> > > > >
> > > > > I was hoping this is known to you or you have something I can verify for you.
> > > >
> > > >
> > > > Thanks, yes.  I believe that both crashes are the same root cause.  The
> > > > cause is that I was not cleaning up after the kmem bulk allocation
> > > > failure on my side.  Please test with this patch.
> > >
> > > Thanks. I applied this patch and hit a LOCKDEP and then a BUG_ON:
> > >
> > >   lib/maple_tree.c:847 suspicious rcu_dereference_protected() usage!
> > >   Call Trace:
> > >    <TASK>
> > >    dump_stack_lvl+0x6c/0x9a
> > >    dump_stack+0x10/0x12
> > >    lockdep_rcu_suspicious+0x12c/0x140
> > >    __mt_destroy+0x96/0xd0
> > >    exit_mmap+0x2a0/0x360
> > >    __mmput+0x34/0x100
> > >    mmput+0x2f/0x40
> > >    free_bprm+0x64/0xe0
> > >    kernel_execve+0x129/0x330
> > >    call_usermodehelper_exec_async+0xd8/0x130
> > >    ? proc_cap_handler+0x210/0x210
> > >    ret_from_fork+0x1f/0x30
> > >    </TASK>
> >
> > Thanks - I'm not sure how this got through, but this should fix it.
> >
> > This should be added to 4236a642ad185 to avoid the LOCKDEP issue.
> >
> > --- a/mm/mmap.c
> > +++ b/mm/mmap.c
> > @@ -3163,9 +3163,9 @@ void exit_mmap(struct mm_struct *mm)
> >
> >         BUG_ON(count != mm->map_count);
> >
> > -       mmap_write_unlock(mm);
> >         trace_exit_mmap(mm);
> >         __mt_destroy(&mm->mm_mt);
> > +       mmap_write_unlock(mm);
> >         vm_unacct_memory(nr_accounted);
> >  }
> 
> Will try this.


Andrew,

Please add this fix to the commit 4236a642ad185 "mm: start tracking VMAs
with maple tree"

I've attached the patch for your convenience.

Thanks,
Liam