Re: slub freelist issue / BUG: unable to handle page fault for address: 000000003ffe0018

Vlastimil Babka
2020-06-05T14:08:37Z

On 6/5/20 3:12 PM, Rafael J. Wysocki wrote:
> On Fri, Jun 5, 2020 at 2:48 PM Vegard Nossum <vegard.nossum@oracle.com> wrote:
>>
>> On 2020-06-05 11:36, Vegard Nossum wrote:
>> >
>> > On 2020-06-05 11:11, Vlastimil Babka wrote:
>> >> On 6/4/20 8:46 PM, Vlastimil Babka wrote:
>> >>> On 6/4/20 7:57 PM, Kees Cook wrote:
>> >>>> On Thu, Jun 04, 2020 at 07:20:18PM +0200, Vegard Nossum wrote:
>> >>>>> On 2020-06-04 19:18, Vlastimil Babka wrote:
>> >>>>>> On 6/4/20 7:14 PM, Vegard Nossum wrote:
>> >>>>>>>
>> >>>>>>> Hi all,
>> >>>>>>>
>> >>>>>>> I ran into a boot problem with latest linus/master
>> >>>>>>> (6929f71e46bdddbf1c4d67c2728648176c67c555) that manifests like this:
>> >>>>>>
>> >>>>>> Hi, what's the .config you use?
>> >>>>>
>> >>>>> Pretty much x86_64 defconfig minus a few options (PCI, USB, ...)
>> >>>>
>> >>>> Oh yes indeed. I immediately crash in the same way with this config.
>> >>>> I'll
>> >>>> start digging...
>> >>>>
>> >>>> (defconfig finishes boot)
>> >>>
>> >>> This is funny, booting with slub_debug=F results in:
>> >>> I'm not sure if it's ACPI or ftrace wrong here, but looks like the
>> >>> changed
>> >>> free pointer offset merely exposes a bug in something else.
>> >>
>> >> So, with Kees' patch reverted, booting with slub_debug=F (or even more
>> >> specific slub_debug=F,ftrace_event_field) also hits this bug below. I
>> >> wanted to bisect it, but v5.7 was also bad, and also v5.6. Didn't try
>> >> further in history. So it's not new at all, and likely very specific to
>> >> your config+QEMU? (and related to the ACPI error messages that precede
>> >> it?).
>> >
>> > I see it too, but not on v5.0. I can bisect it.
>>
>> commit 67a72420a326b45514deb3f212085fb2cd1595b5
>> Author: Bob Moore <robert.moore@intel.com>
>> Date: Fri Aug 16 14:43:21 2019 -0700
>>
>> ACPICA: Increase total number of possible Owner IDs
>>
>> ACPICA commit 1f1652dad88b9d767767bc1f7eb4f7d99e6b5324
>>
>> From 255 to 4095 possible IDs.
>>
>> Link: https://github.com/acpica/acpica/commit/1f1652da
>> Reported-by: Hedi Berriche <hedi.berriche @hpe.com>
>> Signed-off-by: Bob Moore <robert.moore@intel.com>
>> Signed-off-by: Erik Schmauss <erik.schmauss@intel.com>
>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> Bob, Erik, did we miss something in that patch?

Maybe the patch just changes layout in a way that exposes the bug.

Anyway the "ftrace_event_field" cache is not really involved, this is just
because of slab merging. After adding "slub_nomerge" to "slub_debug=F", it
starts making more sense, as the cache becomes Acpi-Namespace

[ 0.140408] ------------[ cut here ]------------
[ 0.140837] cache_from_obj: Wrong slab cache. Acpi-Namespace but object is from kmalloc-64
[ 0.141406] WARNING: CPU: 0 PID: 1 at mm/slab.h:524 kmem_cache_free+0x1d3/0x250
[ 0.142105] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.7.0+ #45
[ 0.142393] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4-rebuilt.opensuse.org 04/01/2014
[ 0.142393] RIP: 0010:kmem_cache_free+0x1d3/0x250
[ 0.142393] Code: 18 4d 85 ed 0f 84 10 ff ff ff 4c 39 ed 74 2f 49 8b 4d 58 48 8b 55 58 48 c7 c6 10 47 a1 ac 48 c7 c7 00 c2 b0 ac e8 b1 cc eb ff <0f> 0b 48 89 de 4c 89 ef e8 10 d7 ff ff 48 8b 15 59 36 9b 00 4c 89
[ 0.142393] RSP: 0018:ffffb39cc0013dc0 EFLAGS: 00010282
[ 0.142393] RAX: 0000000000000000 RBX: ffff937287409e00 RCX: 0000000000000000
[ 0.142393] RDX: 0000000000000001 RSI: 0000000000000092 RDI: ffffffffacfdd32c
[ 0.142393] RBP: ffff93728742ef00 R08: ffffb39cc0013c7d R09: 00000000000000fc
[ 0.142393] R10: ffffb39cc0013c78 R11: ffffb39cc0013c7d R12: ffff937307409e00
[ 0.142393] R13: ffff937287401d00 R14: 0000000000000000 R15: 0000000000000000
[ 0.142393] FS: 0000000000000000(0000) GS:ffff937287a00000(0000) knlGS:0000000000000000
[ 0.142393] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 0.142393] CR2: 0000000000000000 CR3: 0000000003a0a000 CR4: 00000000003406f0
[ 0.142393] Call Trace:
[ 0.142393] acpi_os_release_object+0x5/0x10
[ 0.142393] acpi_ns_delete_children+0x46/0x59
[ 0.142393] acpi_ns_delete_namespace_subtree+0x5c/0x79
[ 0.142393] ? acpi_sleep_proc_init+0x1f/0x1f
[ 0.142393] acpi_ns_terminate+0xc/0x31
[ 0.142393] acpi_ut_subsystem_shutdown+0x45/0xa3
[ 0.142393] ? acpi_sleep_proc_init+0x1f/0x1f
[ 0.142393] acpi_terminate+0x5/0xf
[ 0.142393] acpi_init+0x27b/0x308
[ 0.142393] ? video_setup+0x79/0x79
[ 0.142393] do_one_initcall+0x7b/0x160
[ 0.142393] kernel_init_freeable+0x190/0x1f2
[ 0.142393] ? rest_init+0x9a/0x9a
[ 0.142393] kernel_init+0x5/0xf6
[ 0.142393] ret_from_fork+0x22/0x30
[ 0.142393] ---[ end trace 3539f236ef812ba1 ]---
[ 0.142396] ------------[ cut here ]------------

I've also changed the warning so it's not printed just once, and also prints tracking info
(see the hunk at the end of my mail, I'll turn this to a proper patch later).

With "slub_debug=FU slub_nomerge" there are now multiple warnings, but they all look the same:

[ 0.143815] ------------[ cut here ]------------
[ 0.144131] cache_from_obj: Wrong slab cache. Acpi-Namespace but object is from kmalloc-64
[ 0.144929] WARNING: CPU: 0 PID: 1 at mm/slab.h:524 kmem_cache_free+0x1d3/0x250
[ 0.145129] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.7.0+ #45
[ 0.145129] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4-rebuilt.opensuse.org 04/01/2014
[ 0.145129] RIP: 0010:kmem_cache_free+0x1d3/0x250
[ 0.145129] Code: 18 4d 85 ed 0f 84 10 ff ff ff 4c 39 ed 74 2f 49 8b 4d 58 48 8b 55 58 48 c7 c6 10 47 c1 8d 48 c7 c7 00 c2 d0 8d e8 b1 cc eb ff <0f> 0b 48 89 de 4c 89 ef e8 10 d7 ff ff 48 8b 15 59 36 9b 00 4c 89
[ 0.145129] RSP: 0018:ffff990b80013dc0 EFLAGS: 00010282
[ 0.145129] RAX: 0000000000000000 RBX: ffff972d474ada80 RCX: 0000000000000000
[ 0.145129] RDX: 0000000000000001 RSI: 0000000000000092 RDI: ffffffff8e1dd32c
[ 0.145129] RBP: ffff972d47425680 R08: ffff990b80013c7d R09: 00000000000000fc
[ 0.145129] R10: ffff990b80013c78 R11: ffff990b80013c7d R12: ffff972dc74ada80
[ 0.145129] R13: ffff972d474038c0 R14: 0000000000000000 R15: 0000000000000000
[ 0.145129] FS: 0000000000000000(0000) GS:ffff972d47a00000(0000) knlGS:0000000000000000
[ 0.145129] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 0.145129] CR2: 0000000000000000 CR3: 000000000660a000 CR4: 00000000003406f0
[ 0.145129] Call Trace:
[ 0.145129] acpi_os_release_object+0x5/0x10
[ 0.145129] acpi_ns_delete_children+0x46/0x59
[ 0.145129] acpi_ns_delete_namespace_subtree+0x5c/0x79
[ 0.145129] ? acpi_sleep_proc_init+0x1f/0x1f
[ 0.145129] acpi_ns_terminate+0xc/0x31
[ 0.145129] acpi_ut_subsystem_shutdown+0x45/0xa3
[ 0.145129] ? acpi_sleep_proc_init+0x1f/0x1f
[ 0.145129] acpi_terminate+0x5/0xf
[ 0.145129] acpi_init+0x27b/0x308
[ 0.145129] ? video_setup+0x79/0x79
[ 0.145129] do_one_initcall+0x7b/0x160
[ 0.145129] kernel_init_freeable+0x190/0x1f2
[ 0.145129] ? rest_init+0x9a/0x9a
[ 0.145129] kernel_init+0x5/0xf6
[ 0.145129] ret_from_fork+0x22/0x30
[ 0.145129] ---[ end trace 574554fca7bd06bb ]---
[ 0.145133] INFO: Allocated in acpi_ns_root_initialize+0xb6/0x2d1 age=58 cpu=0 pid=0
[ 0.145881] kmem_cache_alloc_trace+0x1a9/0x1c0
[ 0.146132] acpi_ns_root_initialize+0xb6/0x2d1
[ 0.146578] acpi_initialize_subsystem+0x65/0xa8
[ 0.147024] acpi_early_init+0x5d/0xd1
[ 0.147132] start_kernel+0x45b/0x518
[ 0.147491] secondary_startup_64+0xb6/0xc0
[ 0.147897] ------------[ cut here ]------------

And it seems ACPI is allocating an object via kmalloc() and then freeing it
via kmem_cache_free(<"Acpi-Namespace" kmem_cache>) which is wrong.

> ./scripts/faddr2line vmlinux 'acpi_ns_root_initialize+0xb6'
acpi_ns_root_initialize+0xb6/0x2d1:
kmalloc at include/linux/slab.h:555
(inlined by) kzalloc at include/linux/slab.h:669
(inlined by) acpi_os_allocate_zeroed at include/acpi/platform/aclinuxex.h:57
(inlined by) acpi_ns_root_initialize at drivers/acpi/acpica/nsaccess.c:102

----8<----
diff --git a/mm/slab.h b/mm/slab.h
index 207c83ef6e06..282e78964018 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -503,6 +503,7 @@ static __always_inline void uncharge_slab_page(struct page *page, int order,
memcg_uncharge_slab(page, order, s);
}

+extern void print_tracking(struct kmem_cache *s, void *object);
static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x)
{
struct kmem_cache *cachep;
@@ -520,9 +521,11 @@ static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x)
return s;

cachep = virt_to_cache(x);
- WARN_ONCE(cachep && !slab_equal_or_root(cachep, s),
+ if (WARN(cachep && !slab_equal_or_root(cachep, s),
"%s: Wrong slab cache. %s but object is from %s\n",
- __func__, s->name, cachep->name);
+ __func__, s->name, cachep->name)) {
+ print_tracking(cachep, x);
+ }
return cachep;
}