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Message-ID: <20160129115214.GM32380@htj.duckdns.org>
Date: Fri, 29 Jan 2016 06:52:14 -0500
From: Tejun Heo <tj@...nel.org>
To: Dmitry Vyukov <dvyukov@...gle.com>
Cc: linux-ide@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
Alan Cox <alan@...rguk.ukuu.org.uk>,
Jeff Garzik <jgarzik@...hat.com>,
Sergei Shtylyov <sshtylyov@...mvista.com>,
syzkaller <syzkaller@...glegroups.com>,
Kostya Serebryany <kcc@...gle.com>,
Alexander Potapenko <glider@...gle.com>,
Sasha Levin <sasha.levin@...cle.com>
Subject: Re: ata: BUG in ata_sff_hsm_move
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.
Thanks.
--
tejun
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