From: Dmitry Vyukov <dvyukov@google.com>
To: Tejun Heo <tj@kernel.org>
Cc: linux-ide@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
Jeff Garzik <jgarzik@redhat.com>,
Sergei Shtylyov <sshtylyov@ru.mvista.com>,
syzkaller <syzkaller@googlegroups.com>,
Kostya Serebryany <kcc@google.com>,
Alexander Potapenko <glider@google.com>,
Sasha Levin <sasha.levin@oracle.com>
Subject: Re: ata: BUG in ata_sff_hsm_move
Date: Fri, 29 Jan 2016 12:59:49 +0100 [thread overview]
Message-ID: <CACT4Y+Y_w3msrTw46T8wGpK-j09e6VAoPFa93JSfm+5_kvBAYQ@mail.gmail.com> (raw)
In-Reply-To: <20160129115214.GM32380@htj.duckdns.org>
On Fri, Jan 29, 2016 at 12:52 PM, Tejun Heo <tj@kernel.org> wrote:
> Hello, Dmitry.
>
> On Thu, Jan 28, 2016 at 12:35:43PM +0100, Dmitry Vyukov wrote:
>> Hello,
>>
>> I episodically hit the following BUG while running syzkaller fuzzer:
>>
>> ata2: protocol 2 task_state 0 (dev_stat 0x41)
>> ------------[ cut here ]------------
>> kernel BUG at drivers/ata/libata-sff.c:1302!
> ...
>> So the unexpected state is HSM_IDLE.
>
> Hmmm... the port interrupt handler checks for IDLE before calling into
> hsm_move, so the only explanation would be that something is resetting
> it to IDLE inbetween. ce7514526742 ("libata: prevent HSM state change
> race between ISR and PIO") describes and fixes the same problem. The
> fix seems correct and I can't find anywhere else where this can
> happen. :(
>
> Can you please post the kernel log leading to the BUG? Also, I don't
> think that condition needs to be BUG. I'll change it to WARN.
Here are two logs, in both cases no kernel messages prior to the bug:
https://gist.githubusercontent.com/dvyukov/5087d633e3620280b6c7/raw/31c9ab1ced92ac5f85cfb15eaf48ec5793c2c3a1/gistfile1.txt
https://gist.githubusercontent.com/dvyukov/825b2e3d5fb80ae08a9a/raw/03c5a4f4c4bd9d0a304a71cda2da4c92f4b7f1ba/gistfile1.txt
next prev parent reply other threads:[~2016-01-29 11:59 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-28 11:35 ata: BUG in ata_sff_hsm_move Dmitry Vyukov
2016-01-29 11:52 ` Tejun Heo
2016-01-29 11:59 ` Dmitry Vyukov [this message]
2016-01-29 12:23 ` Tejun Heo
2016-01-29 13:18 ` Dmitry Vyukov
2016-01-29 13:40 ` Dmitry Vyukov
2016-01-29 18:14 ` David Milburn
2016-01-29 20:24 ` Tejun Heo
2016-01-29 20:23 ` Tejun Heo
2016-02-01 10:46 ` Dmitry Vyukov
2016-02-01 16:50 ` [PATCH libata/for-4.5-fixes] libata: fix sff host state machine locking while polling Tejun Heo
2016-01-29 12:20 ` [PATCH libata/for-4.5-fixes] libata-sff: use WARN instead of BUG on illegal host state machine state Tejun Heo
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