linux-kernel - Re: mm: kernel BUG at mm/memory.c:1230

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Date:	Thu, 24 May 2012 12:07:27 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Sasha Levin <levinsasha928@...il.com>
Cc:	viro <viro@...iv.linux.org.uk>, oleg@...hat.com,
	"a.p.zijlstra" <a.p.zijlstra@...llo.nl>, mingo <mingo@...nel.org>,
	Dave Jones <davej@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: mm: kernel BUG at mm/memory.c:1230

On Thu, 24 May 2012 20:27:34 +0200
Sasha Levin <levinsasha928@...il.com> wrote:

> Hi all,
> 
> During fuzzing with trinity inside a KVM tools guest, using latest linux-next, I've stumbled on the following:
> 
> [ 2043.098949] ------------[ cut here ]------------
> [ 2043.099014] kernel BUG at mm/memory.c:1230!

That's

	VM_BUG_ON(!rwsem_is_locked(&tlb->mm->mmap_sem));

in zap_pmd_range()?

> [ 2043.099014] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
> [ 2043.111029] CPU 3 
> [ 2043.111029] Pid: 26853, comm: trinity Tainted: G        W    3.4.0-next-20120524-sasha-00003-ge89ff01 #281  
> [ 2043.111029] RIP: 0010:[<ffffffff811f14d2>]  [<ffffffff811f14d2>] unmap_page_range+0x232/0x3b0
> [ 2043.111029] RSP: 0018:ffff880030349ce8  EFLAGS: 00010246
> [ 2043.111029] RAX: ffff880000025000 RBX: ffff8800266bc000 RCX: 00003ffffffff000
> [ 2043.111029] RDX: ffff880000000000 RSI: ffff88003028cfc0 RDI: 000000006de001e0
> [ 2043.111029] RBP: ffff880030349d68 R08: 0000000100001000 R09: 0000000000000000
> [ 2043.111029] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000100000000
> [ 2043.111029] R13: 0000000100001000 R14: ffff880030349e08 R15: 0000000100000fff
> [ 2043.111029] FS:  0000000000000000(0000) GS:ffff880035a00000(0000) knlGS:0000000000000000
> [ 2043.111029] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [ 2043.111029] CR2: 0000000000000ffc CR3: 0000000013480000 CR4: 00000000000406e0
> [ 2043.111029] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [ 2043.111029] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> [ 2043.111029] Process trinity (pid: 26853, threadinfo ffff880030348000, task ffff88002ed68000)
> [ 2043.111029] Stack:
> [ 2043.111029]  ffffffff811f0b55 0000000100000000 0000000100000fff 0000000100001000
> [ 2043.111029]  ffff880013480000 0000000100000fff 0000000000000000 ffff88003028cfc0
> [ 2043.111029]  ffff8800142b0020 0000000100001000 ffff880030349d58 ffff88003028cfc0
> [ 2043.111029] Call Trace:
> [ 2043.111029]  [<ffffffff811f0b55>] ? follow_page+0x315/0x5a0
> [ 2043.111029]  [<ffffffff811f1719>] unmap_single_vma+0xc9/0xe0
> [ 2043.111029]  [<ffffffff811f1792>] unmap_vmas+0x62/0xa0
> [ 2043.111029]  [<ffffffff811f77a9>] exit_mmap+0xc9/0x170
> [ 2043.111029]  [<ffffffff81225ae5>] ? __khugepaged_exit+0xd5/0x140
> [ 2043.111029]  [<ffffffff810cf719>] mmput+0x89/0xe0
> [ 2043.111029]  [<ffffffff810d5f7b>] exit_mm+0x11b/0x130
> [ 2043.111029]  [<ffffffff82f71b99>] ? _raw_spin_unlock_irq+0x59/0x80
> [ 2043.111029]  [<ffffffff810d8933>] do_exit+0x263/0x510
> [ 2043.111029]  [<ffffffff810d8c81>] do_group_exit+0xa1/0xe0
> [ 2043.111029]  [<ffffffff810d8cd2>] sys_exit_group+0x12/0x20
> [ 2043.111029]  [<ffffffff82f72bf9>] system_call_fastpath+0x16/0x1b
> [ 2043.111029] Code: 00 48 89 f8 66 66 66 90 84 c0 0f 89 89 00 00 00 4c 89 c0 4c 29 e0 48 3d 00 00 20 00 74 5b 49 8b 06 48 83 b8 a8 00 00 00 00 75 0e <0f> 0b 0f 1f 40 00 eb fe 66 0f 1f 44 00 00 48 8b 3b 48 83 3d 85 
> [ 2043.111029] RIP  [<ffffffff811f14d2>] unmap_page_range+0x232/0x3b0
> [ 2043.111029]  RSP <ffff880030349ce8>

The assertion was added in Jan 2011 by 14d1a55cd26f1860 ("thp: add
debug checks for mapcount related invariants").  AFAICT it's just wrong
on the exit path.  Unclear why it's triggering now...

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