Re: [PATCH 01/11] pagewalk: update page table walker core

From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
To: levinsasha928@gmail.com
Cc: linux-mm@kvack.org, akpm@linux-foundation.org, mpm@selenic.com,
	cpw@sgi.com, kosaki.motohiro@jp.fujitsu.com, hannes@cmpxchg.org,
	kamezawa.hiroyu@jp.fujitsu.com, mhocko@suse.cz,
	aneesh.kumar@linux.vnet.ibm.com, xemul@parallels.com,
	riel@redhat.com, kirill.shutemov@linux.intel.com,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 01/11] pagewalk: update page table walker core
Date: Thu, 20 Feb 2014 22:20:55 -0500	[thread overview]
Message-ID: <5306c62f.093d0f0a.3580.fffff796SMTPIN_ADDED_BROKEN@mx.google.com> (raw)
In-Reply-To: <5306942C.2070902@gmail.com>

Hi Sasha,

On Thu, Feb 20, 2014 at 06:47:56PM -0500, Sasha Levin wrote:
> Hi Naoya,
> 
> This patch seems to trigger a NULL ptr deref here. I didn't have a change to look into it yet
> but here's the spew:

Thanks for reporting.
I'm not sure what caused this bug from the kernel message. But in my guessing,
it seems that the NULL pointer is deep inside lockdep routine __lock_acquire(),
so if we find out which pointer was NULL, it might be useful to bisect which
the proble is (page table walker or lockdep, or both.)

BTW, just from curiousity, in my build environment many of kernel functions
are inlined, so should not be shown in kernel message. But in your report
we can see the symbols like walk_pte_range() and __lock_acquire() which never
appear in my kernel. How did you do it? I turned off CONFIG_OPTIMIZE_INLINING,
but didn't make it.

Thanks,
Naoya Horiguchi

> 
> [  281.650503] BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
> [  281.651577] IP: [<ffffffff811a31fc>] __lock_acquire+0xbc/0x580
> [  281.652453] PGD 40b88d067 PUD 40b88c067 PMD 0
> [  281.653143] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
> [  281.653869] Dumping ftrace buffer:
> [  281.654430]    (ftrace buffer empty)
> [  281.654975] Modules linked in:
> [  281.655441] CPU: 4 PID: 12314 Comm: trinity-c361 Tainted: G
> W 3.14.0-rc3-next-20140220-sasha-00008-gab7e7ac-dirty #113
> [  281.657622] task: ffff8804242ab000 ti: ffff880424348000 task.ti: ffff880424348000
> [  281.658503] RIP: 0010:[<ffffffff811a31fc>]  [<ffffffff811a31fc>] __lock_acquire+0xbc/0x580
> [  281.660025] RSP: 0018:ffff880424349ab8  EFLAGS: 00010002
> [  281.660761] RAX: 0000000000000086 RBX: 0000000000000018 RCX: 0000000000000000
> [  281.660761] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000018
> [  281.660761] RBP: ffff880424349b28 R08: 0000000000000001 R09: 0000000000000000
> [  281.660761] R10: 0000000000000001 R11: 0000000000000001 R12: ffff8804242ab000
> [  281.660761] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000001
> [  281.660761] FS:  00007f36534b0700(0000) GS:ffff88052bc00000(0000) knlGS:0000000000000000
> [  281.660761] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [  281.660761] CR2: 0000000000000018 CR3: 000000040b88e000 CR4: 00000000000006e0
> [  281.660761] Stack:
> [  281.660761]  ffff880424349ae8 ffffffff81180695 ffff8804242ab038 0000000000000004
> [  281.660761]  00000000001d8500 ffff88052bdd8500 ffff880424349b18 ffffffff81180915
> [  281.660761]  ffffffff876a68b0 ffff8804242ab000 0000000000000000 0000000000000001
> [  281.660761] Call Trace:
> [  281.660761]  [<ffffffff81180695>] ? sched_clock_local+0x25/0x90
> [  281.660761]  [<ffffffff81180915>] ? sched_clock_cpu+0xc5/0x110
> [  281.660761]  [<ffffffff811a3842>] lock_acquire+0x182/0x1d0
> [  281.660761]  [<ffffffff812990d8>] ? walk_pte_range+0xb8/0x170
> [  281.660761]  [<ffffffff811a3daa>] ? __lock_release+0x1da/0x1f0
> [  281.660761]  [<ffffffff8438ae5b>] _raw_spin_lock+0x3b/0x70
> [  281.660761]  [<ffffffff812990d8>] ? walk_pte_range+0xb8/0x170
> [  281.660761]  [<ffffffff812990d8>] walk_pte_range+0xb8/0x170
> [  281.660761]  [<ffffffff812993a1>] walk_pmd_range+0x211/0x240
> [  281.660761]  [<ffffffff812994fb>] walk_pud_range+0x12b/0x160
> [  281.660761]  [<ffffffff81299639>] walk_pgd_range+0x109/0x140
> [  281.660761]  [<ffffffff812996a5>] __walk_page_range+0x35/0x40
> [  281.660761]  [<ffffffff81299862>] walk_page_range+0xf2/0x130
> [  281.660761]  [<ffffffff812a8ccc>] queue_pages_range+0x6c/0x90
> [  281.660761]  [<ffffffff812a8d80>] ? queue_pages_hugetlb+0x90/0x90
> [  281.660761]  [<ffffffff812a8cf0>] ? queue_pages_range+0x90/0x90
> [  281.660761]  [<ffffffff812a8f50>] ? change_prot_numa+0x30/0x30
> [  281.660761]  [<ffffffff812ac9f1>] do_mbind+0x311/0x330
> [  281.660761]  [<ffffffff811815c1>] ? vtime_account_user+0x91/0xa0
> [  281.660761]  [<ffffffff8124f1a8>] ? context_tracking_user_exit+0xa8/0x1c0
> [  281.660761]  [<ffffffff812aca99>] SYSC_mbind+0x89/0xb0
> [  281.660761]  [<ffffffff812acac9>] SyS_mbind+0x9/0x10
> [  281.660761]  [<ffffffff84395360>] tracesys+0xdd/0xe2
> [  281.660761] Code: c2 04 47 49 85 be fa 0b 00 00 48 c7 c7 bb 85 49
> 85 e8 d9 7b f9 ff 31 c0 e9 9c 04 00 00 66 90 44 8b 1d a9 b8 ac 04 45
> 85 db 74 0c <48> 81 3b 40 61 3f 87 75 06 0f 1f 00 45 31 c0 83 fe 01
> 77 0c 89
> [  281.660761] RIP  [<ffffffff811a31fc>] __lock_acquire+0xbc/0x580
> [  281.660761]  RSP <ffff880424349ab8>
> [  281.660761] CR2: 0000000000000018
> [  281.660761] ---[ end trace b6e188d329664196 ]---
> 
> Thanks,
> Sasha
> 
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