linux-kernel - Re: x86: bad pte in pageattr

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Date:	Mon, 11 Apr 2016 11:47:19 +0200
From:	Dmitry Vyukov <dvyukov@...gle.com>
To:	Andrey Ryabinin <ryabinin.a.a@...il.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"x86@...nel.org" <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	syzkaller <syzkaller@...glegroups.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Sasha Levin <sasha.levin@...cle.com>
Subject: Re: x86: bad pte in pageattr_test

On Mon, Apr 11, 2016 at 11:32 AM, Andrey Ryabinin
<ryabinin.a.a@...il.com> wrote:
>
>
> On 04/11/2016 12:03 PM, Dmitry Vyukov wrote:
>> On Mon, Apr 11, 2016 at 10:52 AM, Andrey Ryabinin
>> <ryabinin.a.a@...il.com> wrote:
>>>
>>>
>>> On 04/11/2016 11:28 AM, Dmitry Vyukov wrote:
>>>> Hello,
>>>>
>>>> I've got the following WARNING while running syzkaller fuzzer:
>>>>
>>>> CPA ffff880054118000: bad pte after revert 8000000054118363
>>>> ------------[ cut here ]------------
>>>> WARNING: CPU: 2 PID: 1503 at arch/x86/mm/pageattr-test.c:226
>>>> pageattr_test+0xa6c/0xd10
>>>> NOT PASSED. Please report.
>>>> Modules linked in:
>>>> CPU: 2 PID: 1503 Comm: pageattr-test Not tainted 4.6.0-rc2+ #346
>>>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>>>>  ffffffff87eb25c0 ffff88003b627a70 ffffffff82c8b17f ffffffff81490b58
>>>>  fffffbfff0fd64b8 ffff88003b627ae8 0000000000000000 ffffffff86a77e00
>>>>  ffffffff8129487c 0000000000000009 ffff88003b627ab8 ffffffff8136639f
>>>> Call Trace:
>>>>  [<     inline     >] __dump_stack lib/dump_stack.c:15
>>>>  [<ffffffff82c8b17f>] dump_stack+0x12e/0x18f lib/dump_stack.c:51
>>>>  [<ffffffff8136639f>] __warn+0x19f/0x1e0 kernel/panic.c:512
>>>>  [<ffffffff8136648c>] warn_slowpath_fmt+0xac/0xd0 kernel/panic.c:527
>>>>  [<ffffffff8129487c>] pageattr_test+0xa6c/0xd10 arch/x86/mm/pageattr-test.c:226
>>>>  [<ffffffff81294b3b>] do_pageattr_test+0x1b/0x60 arch/x86/mm/pageattr-test.c:240
>>>>  [<ffffffff813cde7f>] kthread+0x23f/0x2d0 drivers/block/aoe/aoecmd.c:1303
>>>
>>> It seems, that your script is buggy. It should be kthread() from kernel/kthread.c here.
>>
>>
>> I probably used a non-matching vmlinux for symbolization.
>
> No, it's a bug in your script. To find out source location, it uses 'function_name + offset' instead of absolute address.
> We have 2 kthread() functions in kernel and this confuses you script.
>
>
> E.g. my vmlinux :
>  $ addr2line -i -e vmlinux ffffffff811b5290
>         /home/andrew/linux/kernel/kthread.c:178
>  $ addr2line -i -e kasan_conf/vmlinux ffffffff825c7240
>         /home/andrew/linux/drivers/block/aoe/aoecmd.c:1289
>
>
>  $ echo '[<ffffffff811b5290>] kthread+0x00/0x00' | python kasan_symbolize.py vmlinux
>         [<ffffffff811b5290>] kthread+0x00/0x00 drivers/block/aoe/aoecmd.c:462
>  $ echo '[<ffffffff825c7240>] kthread+0x00/0x00' | python kasan_symbolize.py vmlinux
>         [<ffffffff825c7240>] kthread+0x00/0x00 drivers/block/aoe/aoecmd.c:462


Agree. Filed https://github.com/google/sanitizers/issues/668
Thanks!

>> Please
>> check the raw report below if the symbolized one does not make sense.
>>
>> \/\/\/\/\/\/\/\/
>>
>>>> For the repcord, full syzkaller log:
>>>> https://gist.githubusercontent.com/dvyukov/323ff7275c5ac38156cb40caeacac057/raw/0836f8dd81024e441f81caebdcb73ca1221aef97/gistfile1.txt