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* [linux-next-20190131] NULL pointer dereference at shrink_node_memcg.
@ 2019-02-01  3:37 Tetsuo Handa
  2019-02-01  4:28 ` Chris Down
  0 siblings, 1 reply; 2+ messages in thread
From: Tetsuo Handa @ 2019-02-01  3:37 UTC (permalink / raw)
  To: Chris Down; +Cc: Johannes Weiner, Roman Gushchin, linux-mm

Commit 8a907cdf0177ab40 ("mm, memcg: proportional memory.{low,min} reclaim")
broke global reclaim by kdump kernel due to NULL pointer dereference at

   protection = mem_cgroup_protection(memcg);

. Please fix.

----------
[    0.000000][    T0] Linux version 5.0.0-rc4-next-20190131 (root@localhost.localdomain) (gcc version 4.8.5 20150623 (Red Hat 4.8.5-36) (GCC)) #280 SMP PREEMPT Fri Feb 1 09:11:44 JST 2019
[    0.000000][    T0] Command line: BOOT_IMAGE=/boot/vmlinuz-5.0.0-rc4-next-20190131 ro security=none sysrq_always_enabled console=ttyS0,115200n8 console=tty0 LANG=en_US.UTF-8 cgroup_no_v1=all irqpoll nr_cpus=1 reset_devices cgroup_disable=memory mce=off numa=off udev.children-max=2 panic=10 rootflags=nofail acpi_no_memhotplug transparent_hugepage=never nokaslr disable_cpu_apicid=0 elfcorehdr=867732K
(...snipped...)
[   28.323429][   T31] BUG: unable to handle kernel NULL pointer dereference at 0000000000000180
[   28.326592][   T31] #PF error: [normal kernel read fault]
[   28.328538][   T31] PGD 274bd067 P4D 274bd067 PUD 276e1067 PMD 0 
[   28.330587][   T31] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
[   28.332627][   T31] CPU: 0 PID: 31 Comm: kswapd0 Not tainted 5.0.0-rc4-next-20190131 #280
[   28.335356][   T31] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 04/13/2018
[   28.338845][   T31] RIP: 0010:shrink_node_memcg+0xa1/0x4d0
[   28.340895][   T31] Code: 49 c7 04 24 00 00 00 00 45 31 f6 49 89 dd 48 8b 44 24 28 48 8b 7c 24 18 44 89 ee 44 89 eb 0f be 50 1b e8 62 bd ff ff 48 89 c6 <49> 8b 87 80 01 00 00 49 8b 97 98 01 00 00 48 39 c2 48 0f 43 c2 48
[   28.347084][   T31] RSP: 0018:ffffc9000011bc10 EFLAGS: 00010246
[   28.349209][   T31] RAX: 0000000000000f8e RBX: 0000000000000000 RCX: 0000000000000003
[   28.351858][   T31] RDX: 0000000000000004 RSI: 0000000000000f8e RDI: ffffffff822fdd68
[   28.354750][   T31] RBP: ffffc9000011bce8 R08: 0000000000000000 R09: ffffffff822fc100
[   28.357437][   T31] R10: 0000000000000000 R11: 0000000000000000 R12: ffffc9000011bd40
[   28.360018][   T31] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
[   28.362825][   T31] FS:  0000000000000000(0000) GS:ffff888034800000(0000) knlGS:0000000000000000
[   28.365961][   T31] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   28.368279][   T31] CR2: 0000000000000180 CR3: 0000000027352004 CR4: 00000000003606b0
[   28.370939][   T31] Call Trace:
[   28.372315][   T31]  ? __lock_acquire+0x959/0x1260
[   28.374140][   T31]  shrink_node+0xd8/0x460
[   28.375847][   T31]  balance_pgdat+0x24d/0x4b0
[   28.377636][   T31]  kswapd+0x1ac/0x5e0
[   28.379302][   T31]  ? wait_woken+0xa0/0xa0
[   28.380938][   T31]  kthread+0x10b/0x140
[   28.382516][   T31]  ? balance_pgdat+0x4b0/0x4b0
[   28.384263][   T31]  ? kthread_cancel_delayed_work_sync+0x10/0x10
[   28.386530][   T31]  ret_from_fork+0x24/0x30
[   28.388196][   T31] Modules linked in: xfs libcrc32c sd_mod sr_mod cdrom serio_raw ahci libahci mptspi ata_generic pata_acpi scsi_transport_spi mptscsih mptbase vmwgfx drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm drm i2c_core ata_piix libata
[   28.395374][   T31] CR2: 0000000000000180
[   28.397135][   T31] ---[ end trace 42d4bab7295e2355 ]---
[   28.399381][   T31] RIP: 0010:shrink_node_memcg+0xa1/0x4d0
[   28.401444][   T31] Code: 49 c7 04 24 00 00 00 00 45 31 f6 49 89 dd 48 8b 44 24 28 48 8b 7c 24 18 44 89 ee 44 89 eb 0f be 50 1b e8 62 bd ff ff 48 89 c6 <49> 8b 87 80 01 00 00 49 8b 97 98 01 00 00 48 39 c2 48 0f 43 c2 48
[   28.408079][   T31] RSP: 0018:ffffc9000011bc10 EFLAGS: 00010246
[   28.410327][   T31] RAX: 0000000000000f8e RBX: 0000000000000000 RCX: 0000000000000003
[   28.412930][   T31] RDX: 0000000000000004 RSI: 0000000000000f8e RDI: ffffffff822fdd68
[   28.415567][   T31] RBP: ffffc9000011bce8 R08: 0000000000000000 R09: ffffffff822fc100
[   28.418284][   T31] R10: 0000000000000000 R11: 0000000000000000 R12: ffffc9000011bd40
[   28.421068][   T31] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
[   28.423683][   T31] FS:  0000000000000000(0000) GS:ffff888034800000(0000) knlGS:0000000000000000
[   28.426549][   T31] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   28.428977][   T31] CR2: 0000000000000180 CR3: 0000000027352004 CR4: 00000000003606b0
----------


^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [linux-next-20190131] NULL pointer dereference at shrink_node_memcg.
  2019-02-01  3:37 [linux-next-20190131] NULL pointer dereference at shrink_node_memcg Tetsuo Handa
@ 2019-02-01  4:28 ` Chris Down
  0 siblings, 0 replies; 2+ messages in thread
From: Chris Down @ 2019-02-01  4:28 UTC (permalink / raw)
  To: Tetsuo Handa; +Cc: Johannes Weiner, Roman Gushchin, linux-mm

Hey Tetsuo,

Tetsuo Handa writes:
>Commit 8a907cdf0177ab40 ("mm, memcg: proportional memory.{low,min} reclaim")
>broke global reclaim by kdump kernel due to NULL pointer dereference at
>
>   protection = mem_cgroup_protection(memcg);
>
>. Please fix.

Oh yeah, memcg is null if memcg is disabled at run time but is compiled in (so 
this works with CONFIG_MEMCG and !CONFIG_MEMCG, but not CONFIG_MEMCG + 
cgroup_disable=memory).

A fix will be out shortly, thanks.


^ permalink raw reply	[flat|nested] 2+ messages in thread

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2019-02-01  3:37 [linux-next-20190131] NULL pointer dereference at shrink_node_memcg Tetsuo Handa
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