Re: 2.6.37-rc7: NULL pointer dereference

[Hugh Dickins]

On Wed, 22 Dec 2010, Johannes Weiner wrote:
> On Thu, Dec 23, 2010 at 12:37:11AM +0900, Minchan Kim wrote:
> > On Wed, Dec 22, 2010 at 9:25 PM, Thomas Meyer <thomas@xxxxxxxx> wrote:
> > > BUG: unable to handle kernel NULL pointer dereference at 00000008
> > > IP: [<c04eae14>] __mem_cgroup_try_charge+0x234/0x430
> > > Process swapoff (pid: 8058, ti=f2e70000 task=f3e55860 task.ti=f2e70000)
> > > Call Trace:
> > >  [<c0456607>] ? ktime_get_ts+0x107/0x140
> > >  [<c04ebb89>] ? mem_cgroup_try_charge_swapin+0x49/0xb0
> > >  [<c04d9b4b>] ? unuse_mm+0x1db/0x300
> > >  [<c04dad9a>] ? sys_swapoff+0x2aa/0x890
> > >  [<c047cd58>] ? audit_syscall_entry+0x218/0x240
> > >  [<c047d043>] ? audit_syscall_exit+0x1f3/0x220
> > >  [<c0403013>] ? sysenter_do_call+0x12/0x22
> 
> This could be explained by a kernel without VM_BUG_ON(), where
> !mm->owner goes uncaught until css_tryget() reads mem.css.flags (eight
> bytes member offset on 32-bit).
> 
> Does
> 	http://marc.info/?l=linux-mm&m=128889198016021&w=2
> help?

I'm sure you're right, Hannes.  Thanks for the prod.  Sadly, Kame
and I both let the fix drift, expecting it to magick its way into
Linus's tree.  We're now at rc8: I'd better change my Acked-by to
a Signed-off-by and try sending it in immediately: will do so now.

Hugh