linux-kernel - Re: mm: gpf in find

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Date:	Sun, 08 Sep 2013 10:11:43 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	Sasha Levin <sasha.levin@...cle.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>, walken@...gle.com,
	riel@...hat.com, hughd@...gle.com, trinity@...r.kernel.org
Subject: Re: mm: gpf in find_vma

Sasha Levin wrote:
> Hi all,
>
> While fuzzing with trinity inside a KVM tools guest, running latest -next kernel, I've
> stumbled on the following:
>
> [13600.008029] general protection fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
> [13600.010235] Modules linked in:
> [13600.010742] CPU: 30 PID: 26329 Comm: kworker/u128:2 Tainted: G W 3.11.0-next-20130906-sasha #3985
> [13600.012301] task: ffff880e54630000 ti: ffff880e52380000 task.ti: ffff880e52380000
> [13600.013553] RIP: 0010:[<ffffffff81258b82>] [<ffffffff81258b82>] find_vma+0x12/0x70
> [13600.014929] RSP: 0018:ffff880e52381c38 EFLAGS: 00010282
> [13600.016808] RAX: f0000040f0000040 RBX: 00007fffffffe000 RCX: ffff880e54630000
> [13600.016808] RDX: 0000000000000000 RSI: 00007fffffffe000 RDI: ffff880000000000
> [13600.016808] RBP: ffff880e52381c38 R08: 0000000000000017 R09: ffff880e52381d70
> [13600.016808] R10: ffff880e52381d70 R11: 0000000000000007 R12: ffff880e54630000
> [13600.016808] R13: ffff880000000000 R14: 000000000000000f R15: 0000000000000000
> [13600.016808] FS: 0000000000000000(0000) GS:ffff880fe3200000(0000) knlGS:0000000000000000
> [13600.016808] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [13600.016808] CR2: 0000000004a66678 CR3: 0000000e520fe000 CR4: 00000000000006e0
> [13600.016808] Stack:
> [13600.016808] ffff880e52381c68 ffffffff8125a36b ffff880fb7d373c8 ffff880fb6f82238
> [13600.016808] ffff880e54630000 ffff880000000000 ffff880e52381d28 ffffffff8125622d
> [13600.016808] ffff880e52381c98 ffffffff84109b7c 00000000b7d373c8 ffff880e52380010
> [13600.016808] Call Trace:
> [13600.016808] [<ffffffff8125a36b>] find_extend_vma+0x2b/0x90
> [13600.016808] [<ffffffff8125622d>] __get_user_pages+0xdd/0x630
> [13600.016808] [<ffffffff84109b7c>] ? _raw_spin_unlock_irqrestore+0x7c/0xa0
> [13600.016808] [<ffffffff81256832>] get_user_pages+0x52/0x60
> [13600.016808] [<ffffffff812adecc>] get_arg_page+0x5c/0x100
> [13600.016808] [<ffffffff812ade58>] ? get_user_arg_ptr+0x58/0x70
> [13600.016808] [<ffffffff812ae084>] copy_strings+0x114/0x260
> [13600.016808] [<ffffffff812ae21b>] copy_strings_kernel+0x4b/0x60
> [13600.016808] [<ffffffff812b0203>] do_execve_common+0x2f3/0x4d0
> [13600.016808] [<ffffffff812b001c>] ? do_execve_common+0x10c/0x4d0
> [13600.016808] [<ffffffff812b04a7>] do_execve+0x37/0x40
> [13600.016808] [<ffffffff81140721>] ____call_usermodehelper+0x111/0x130
> [13600.016808] [<ffffffff8115f270>] ? schedule_tail+0x30/0xb0
> [13600.016808] [<ffffffff81140610>] ? __call_usermodehelper+0xb0/0xb0
> [13600.016808] [<ffffffff841125ec>] ret_from_fork+0x7c/0xb0
> [13600.016808] [<ffffffff81140610>] ? __call_usermodehelper+0xb0/0xb0
> [13600.016808] Code: 40 20 83 f0 01 83 e0 01 eb 09 0f 1f 80 00 00 00 00 31 c0 c9 c3 0f 1f 40 00 55 48 89 e5 66 66 66 66
> 90 48 8b 47 10 48 85 c0 74 0b <48> 39 70 08 76 05 48 3b 30 73 4d 48 8b 57 08 31 c0 48 85 d2 74
> [13600.016808] RIP [<ffffffff81258b82>] find_vma+0x12/0x70
> [13600.016808] RSP <ffff880e52381c38>
>
> The disassembly is:
>
> /* Check the cache first. */
> /* (Cache hit rate is typically around 35%.) */
> vma = ACCESS_ONCE(mm->mmap_cache);
> 1f9: 48 8b 47 10 mov 0x10(%rdi),%rax
> if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) {
> 1fd: 48 85 c0 test %rax,%rax
> 200: 74 0b je 20d <find_vma+0x1d>
> 202: 48 39 70 08 cmp %rsi,0x8(%rax) <--- here
> 206: 76 05 jbe 20d <find_vma+0x1d>
> 208: 48 3b 30 cmp (%rax),%rsi
> 20b: 73 4d jae 25a <find_vma+0x6a>
>
>
> Note that I've started seeing this when I started testing with 64 vcpus.

mm_struct pointer (%rdi) 0xffff880000000000 looks suspicious =)

>
>
> Thanks,
> Sasha
>
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