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Date: Mon, 9 Sep 2013 11:39:49 +0900
From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Sasha Levin <sasha.levin@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, mhocko@suse.cz,
        dhillf@gmail.com, liwanp@linux.vnet.ibm.com,
        LKML <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>, trinity@vger.kernel.org,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        aneesh.kumar@linux.vnet.ibm.com
Subject: Re: hugetlb: NULL ptr deref in region_truncate
Message-ID: <20130909023949.GA22390@lge.com>
References: <522C8DA8.6030701@oracle.com>
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On Sun, Sep 08, 2013 at 10:46:00AM -0400, Sasha Levin wrote:
> Hi all,
> 
> While fuzzing with trinity inside a KVM tools guest, running latest -next kernel, I've
> stumbled on the following:
> 
> [  998.281867] BUG: unable to handle kernel NULL pointer dereference at 0000000000000274
> [  998.283333] IP: [<ffffffff812707c4>] region_truncate+0x64/0xd0
> [  998.284288] PGD 0
> [  998.284717] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
> [  998.286506] Modules linked in:
> [  998.287101] CPU: 88 PID: 24650 Comm: trinity-child85 Tainted: G
> B   W 3.11.0-next-20130906-sasha #3985
> [  998.288844] task: ffff8800c1110000 ti: ffff8800c544a000 task.ti: ffff8800c544a000
> [  998.290257] RIP: 0010:[<ffffffff812707c4>]  [<ffffffff812707c4>] region_truncate+0x64/0xd0
> [  998.290301] RSP: 0018:ffff8800c544ba58  EFLAGS: 00010293
> [  998.290301] RAX: 0000000000000274 RBX: ffff880f47d3b0f8 RCX: 000000003fd075fc
> [  998.290301] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff880f47d3b0f8
> [  998.290301] RBP: ffff8800c544ba78 R08: 0000000000000000 R09: 0000000000000000
> [  998.290301] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> [  998.290301] R13: ffffffff8741bc60 R14: 0000000000000000 R15: ffff880e9d8b5590
> [  998.290301] FS:  00007f47f28c2700(0000) GS:ffff880fe2200000(0000) knlGS:0000000000000000
> [  998.290301] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  998.290301] CR2: 0000000000000274 CR3: 0000000005a23000 CR4: 00000000000006e0
> [  998.290301] Stack:
> [  998.290301]  ffff880f47d3ad50 0000000000000000 ffffffff8741bc60 0000000000000000
> [  998.290301]  ffff8800c544bac8 ffffffff81274856 0000000000000000 ffff8800c544bb18
> [  998.290301]  0000000000000000 0000000000000000 0000000000000000 ffff8800c544bb18
> [  998.290301] Call Trace:
> [  998.290301]  [<ffffffff81274856>] hugetlb_unreserve_pages+0x46/0xd0
> [  998.290301]  [<ffffffff8142abe2>] truncate_hugepages+0x202/0x220
> [  998.290301]  [<ffffffff812d2ec8>] ? inode_wait_for_writeback+0x28/0x50
> [  998.290301]  [<ffffffff81150fe7>] ? bit_waitqueue+0x17/0xc0
> [  998.290301]  [<ffffffff812d2ed8>] ? inode_wait_for_writeback+0x38/0x50
> [  998.290301]  [<ffffffff8142ac18>] hugetlbfs_evict_inode+0x18/0x30
> [  998.290301]  [<ffffffff812c4001>] evict+0xc1/0x1a0
> [  998.290301]  [<ffffffff812c4243>] iput_final+0x163/0x180
> [  998.290301]  [<ffffffff812c42af>] iput+0x4f/0x60
> [  998.290301]  [<ffffffff812bf5a8>] dentry_iput+0xc8/0xf0
> [  998.290301]  [<ffffffff812c200a>] dput+0x17a/0x1a0
> [  998.290301]  [<ffffffff812a9ea7>] __fput+0x2b7/0x2d0
> [  998.290301]  [<ffffffff812a9f8e>] ____fput+0xe/0x10
> [  998.290301]  [<ffffffff81149b4e>] task_work_run+0xae/0xf0
> [  998.290301]  [<ffffffff81127c09>] do_exit+0x2d9/0x4d0
> [  998.290301]  [<ffffffff81127ea9>] do_group_exit+0xa9/0xe0
> [  998.290301]  [<ffffffff8113c185>] get_signal_to_deliver+0x475/0x4d0
> [  998.290301]  [<ffffffff81067c2b>] do_signal+0x4b/0x120
> [  998.290301]  [<ffffffff8114ba24>] ? __rcu_read_unlock+0x44/0x80
> [  998.290301]  [<ffffffff8116911c>] ? vtime_account_user+0x5c/0x70
> [  998.290301]  [<ffffffff81222215>] ? context_tracking_user_exit+0x145/0x150
> [  998.290301]  [<ffffffff81067f8a>] do_notify_resume+0x5a/0xe0
> [  998.290301]  [<ffffffff841129a0>] int_signal+0x12/0x17
> [  998.290301] Code: 0e 48 8b 00 48 39 d8 75 ee eb 6c 0f 1f 40 00 45
> 31 f6 48 3b 70 10 90 7e 0e 4c 8b 70 18 48 89 70 18 49 29 f6 48 8b 00
> 48 8b 40 08 <4c> 8b 28 4d 8b 65 00 4c 89 ef 4d 3b 6d 08 74 44 4c 39
> eb 75 12
> [  998.290301] RIP  [<ffffffff812707c4>] region_truncate+0x64/0xd0
> [  998.290301]  RSP <ffff8800c544ba58>
> [  998.290301] CR2: 0000000000000274

More ccing to experts.

It looks like region tracking list corruption,
but I'm not sure that it is related to recent changes,
because, theoretically, the race is possible on region tracking long time ago.

Sasha, Is it easily reproducible?
If so, could you tell me how to reproduce it?

Thanks.
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