linux-kernel - Re: possible deadlock in __ata_sff

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Message-ID: <Y5s7F/4WKe8BtftB@ZenIV>
Date:   Thu, 15 Dec 2022 15:19:51 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>
Cc:     Wei Chen <harperchen1110@...il.com>, linux-ide@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        syzbot <syzkaller@...glegroups.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Chuck Lever <chuck.lever@...cle.com>,
        Jeff Layton <jlayton@...nel.org>
Subject: Re: possible deadlock in __ata_sff_interrupt

On Thu, Dec 15, 2022 at 06:48:20PM +0900, Damien Le Moal wrote:

> The problem is here: sg_rq_end_io() calling kill_fasync(). But at a quick
> glance, this is not the only driver calling kill_fasync() with a spinlock
> held with irq disabled... So there may be a fundamental problem with
> kill_fasync() function if drivers are allowed to do that, or the reverse,
> all drivers calling that function with a lock held with irq disabled need
> to be fixed.
> 
> Al, Chuck, Jeff,
> 
> Any thought ?

What is the problem with read_lock_irqsave() called with irqs disabled?
read_lock_irq() would have been a bug in such conditions, of course, but
that's not what we use...