linux-kernel - [linux-next] do_task_stat: BUG: unable to handle kernel paging request at ffffc9000041bfd8

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Date:   Tue, 27 Sep 2016 09:45:56 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     luto@...capital.net
Cc:     linux-kernel@...r.kernel.org
Subject: [linux-next] do_task_stat: BUG: unable to handle kernel paging request at ffffc9000041bfd8

Hello.

I'm hitting below bug when a process $pid terminates while somebody else is reading
/proc/$pid/stat . According to https://lkml.org/lkml/2016/8/21/10 , it was already
fixed. But it seems to me that this bug is still in linux-next-20160923.
Is this a different bug?

[  191.915694] BUG: unable to handle kernel paging request at ffffc9000041bfd8
[  191.917803] IP: [<ffffffff811e3401>] do_task_stat+0x951/0xb90
[  191.919477] PGD 7e051067 PUD 7e052067 PMD 36ae6067 PTE 0
[  191.921029] Oops: 0000 [#1] PREEMPT SMP
[  191.922167] Modules linked in: ebtable_nat ebtable_broute bridge stp llc ebtable_filter ebtables coretemp pcspkr sg i2c_piix4 sd_mod ata_generic pata_acpi serio_raw ahci libahci e1000 mptspi scsi_transport_spi mptscsih mptbase ata_piix vmwgfx drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm drm i2c_core libata
[  191.931246] CPU: 0 PID: 10894 Comm: oom_preempt2 Not tainted 4.8.0-rc7-next-20160923+ #472
[  191.933683] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/02/2015
[  191.936572] task: ffff88007698ce80 task.stack: ffffc90004fe4000
[  191.938425] RIP: 0010:[<ffffffff811e3401>]  [<ffffffff811e3401>] do_task_stat+0x951/0xb90
[  191.940678] RSP: 0018:ffffc90004fe7c40  EFLAGS: 00010202
[  191.942273] RAX: ffffc9000041c000 RBX: ffff8800790060c0 RCX: 0000000000000000
[  191.944404] RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff88007913ef00
[  191.946369] RBP: ffffc90004fe7d60 R08: 0000000000000001 R09: 0000000000000000
[  191.948502] R10: 0000000000000001 R11: 0000000000000000 R12: ffff88007913ef00
[  191.950577] R13: ffff8800773913c0 R14: 0000000000000001 R15: ffffffff81a28da0
[  191.952923] FS:  00007f56f12bb740(0000) GS:ffff88007ea00000(0000) knlGS:0000000000000000
[  191.955128] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  191.957154] CR2: ffffc9000041bfd8 CR3: 0000000079d18000 CR4: 00000000001406f0
[  191.959227] Stack:
[  191.960242]  00000000000028e0 0000000000000401 0000000000000000 0000000000438000
[  191.962471]  ffff8800794ee500 000000000000000a 00000000000028e0 0000000000000000
[  191.964715]  00000000000028e0 ffffffffffffffff 0000000000000000 0000000000000000
[  191.967027] Call Trace:
[  191.968340]  [<ffffffff811e401f>] proc_tgid_stat+0xf/0x20
[  191.970087]  [<ffffffff811de5fb>] proc_single_show+0x4b/0x80
[  191.971900]  [<ffffffff811a0650>] seq_read+0x100/0x380
[  191.973578]  [<ffffffff8117a6e2>] __vfs_read+0x32/0x130
[  191.975280]  [<ffffffff8127e87e>] ? security_file_permission+0x9e/0xc0
[  191.977290]  [<ffffffff8117b249>] vfs_read+0x89/0x130
[  191.978981]  [<ffffffff8117c892>] SyS_pread64+0x82/0xb0
[  191.980761]  [<ffffffff8100241c>] do_syscall_64+0x5c/0x170
[  191.982682]  [<ffffffff816002c6>] entry_SYSCALL64_slow_path+0x25/0x25
[  191.984657] Code: ff e8 84 11 ea ff 48 8b 85 50 ff ff ff 49 03 87 b8 01 00 00 48 89 85 50 ff ff ff e9 e8 f8 ff ff 49 8b 84 24 58 08 00 00 4c 89 e7 <48> 8b 40 d8 48 89 85 48 ff ff ff e8 af 69 e3 ff 48 89 85 40 ff 
[  191.991974] RIP  [<ffffffff811e3401>] do_task_stat+0x951/0xb90
[  191.993931]  RSP <ffffc90004fe7c40>
[  191.995383] CR2: ffffc9000041bfd8
[  191.997003] ---[ end trace 8bdf0d4222ebcddb ]---

I can't find a patch titled "[DEBUG] forcibly free stacks immediately" in linux-next.
Which patch should I try reverting?