Re: [BUG -next 20181008] list corruption with "mm/slub: remove useless condition in deactivate_slab"

[Pingfan Liu]

Hi heiko,

On Mon, Oct 15, 2018 at 1:54 PM Pingfan Liu <kernelfans@xxxxxxxxx> wrote:
>
> On Tue, Oct 9, 2018 at 2:35 PM Heiko Carstens <heiko.carstens@xxxxxxxxxx> wrote:
> >
> > Hello,
> >
> > with linux-next for 20181008 I can reliably crash my system with lot's of
> > debugging options enabled on s390. List debugging triggers the list
> > corruption below, which I could bisect down to this commit:
> >
> > fde06e07750477f049f12d7d471ffa505338a3e7 is the first bad commit
> > commit fde06e07750477f049f12d7d471ffa505338a3e7
> > Author: Pingfan Liu <kernelfans@xxxxxxxxx>
> > Date:   Thu Oct 4 07:43:01 2018 +1000
> >
> >     mm/slub: remove useless condition in deactivate_slab
> >
> >     The var l should be used to reflect the original list, on which the page
> >     should be.  But c->page is not on any list.  Furthermore, the current code
> >     does not update the value of l.  Hence remove the related logic
> >
> >     Link: http://lkml.kernel.org/r/1537941430-16217-1-git-send-email-kernelfans@xxxxxxxxx
> >     Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx>
> >     Acked-by: Christoph Lameter <cl@xxxxxxxxx>
> >     Cc: Pekka Enberg <penberg@xxxxxxxxxx>
> >     Cc: David Rientjes <rientjes@xxxxxxxxxx>
> >     Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
> >     Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> >     Signed-off-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> >
> > list_add double add: new=000003d1029ecc08, prev=000000008ff846d0,next=000003d1029ecc08.
> > ------------[ cut here ]------------
> > kernel BUG at lib/list_debug.c:31!
> > illegal operation: 0001 ilc:1 [#1] PREEMPT SMP
> > Modules linked in:
> > CPU: 3 PID: 106 Comm: (sd-executor) Not tainted 4.19.0-rc6-00291-gfde06e077504 #21
> > Hardware name: IBM 2964 NC9 702 (z/VM 6.4.0)
> > Krnl PSW : (____ptrval____) (____ptrval____) (__list_add_valid+0x98/0xa8)
> >            R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:3 CC:1 PM:0 RI:0 EA:3
> > Krnl GPRS: 0000000074311fdf 0000000080000001 0000000000000058 0000000000e7b8b2
> >            0000000000000000 0000000075438c64 00000000a7b31928 001c007b00000000
> >            000000008fe99d00 00000000a7b31b40 000003d1029ecc08 00000000a7c03a80
> >            000003d1029ecc08 000000008ff84680 00000000007b5674 00000000a7c03960
> > Krnl Code: 00000000007b5668: c0200034734a        larl    %r2,e43cfc
> >            00000000007b566e: c0e5ffd0cf51        brasl   %r14,1cf510
> >           #00000000007b5674: a7f40001            brc     15,7b5676
> >           >00000000007b5678: a7290001            lghi    %r2,1
> >            00000000007b567c: ebcff0a00004        lmg     %r12,%r15,160(%r15)
> >            00000000007b5682: 07fe                bcr     15,%r14
> >            00000000007b5684: 0707                bcr     0,%r7
> >            00000000007b5686: 0707                bcr     0,%r7
> > Call Trace:
> > ([<00000000007b5674>] __list_add_valid+0x94/0xa8)
> >  [<000000000037d30e>] deactivate_slab.isra.15+0x45e/0x810
> >  [<000000000037ede4>] ___slab_alloc+0x76c/0x7c0
> >  [<000000000037eeb0>] __slab_alloc.isra.16+0x78/0xa8
> >  [<00000000003808c8>] kmem_cache_alloc+0x160/0x458
> >  [<0000000000141a3a>] vm_area_dup+0x3a/0x60
> >  [<0000000000142f0a>] copy_process+0xd72/0x2100
> >  [<000000000014449a>] _do_fork+0xba/0x688
> >  [<0000000000144bb0>] sys_clone+0x48/0x50
> >  [<0000000000b8faf0>] system_call+0xd8/0x2d0
> > INFO: lockdep is turned off.
> > Last Breaking-Event-Address:
> >  [<00000000007b5674>] __list_add_valid+0x94/0xa8
> >
> > Kernel panic - not syncing: Fatal exception: panic_on_oops
> >
>
> Sorry that just see this email, and reply late.
> I think it is caused by the uinon page->lru and page->next. It can be fixed by:
> diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
> index 3a1a1db..4aa0fb5 100644
> --- a/include/linux/slub_def.h
> +++ b/include/linux/slub_def.h
> @@ -56,6 +56,7 @@ struct kmem_cache_cpu {
>  #define slub_set_percpu_partial(c, p)          \
>  ({                                             \
>         slub_percpu_partial(c) = (p)->next;     \
> +       p->next = NULL; \
>  })
>
> I will do some test and post the fix.
>
Please ignore the above comment. And after re-check the code, I am
sure that all callers of deactivate_slab(), pass c->page, which means
that page should not be on any list. But your test result "list_add
double add: new=000003d1029ecc08,
prev=000000008ff846d0,next=000003d1029ecc08"  indicates that
page(new) is already on a list. I think that maybe something else is
wrong which is covered.
I can not reproduce this bug on x86. Could you share your config and
cmdline? Any do you turn on any debug option of slub?

Thanks,
Pingfan