linux-kernel - Re: Potential race condition in drivers/ata/sata

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Message-ID: <20160810035133.GD25053@mtj.duckdns.org>
Date:	Tue, 9 Aug 2016 23:51:33 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Pavel Andrianov <andrianov@...ras.ru>
Cc:	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
	ldv-project@...uxtesting.org,
	Vaishali Thakkar <vaishali.thakkar@...cle.com>
Subject: Re: Potential race condition in drivers/ata/sata_mv.ko

Hello,

On Fri, Aug 05, 2016 at 03:43:30PM +0300, Pavel Andrianov wrote:
> In drivers/ata/sata_mv.ko function mv_set_main_irq_mask is called several
> times. Twice with a spinlock, twice from init function and once without any
> protection. The call without protection rises to several handlers from
> ata_port_operations. The structure with the ata_port_operations is included
> into a structure 'host' in mv_platform_probe and in mv_pci_init_one. At the
> end of these functions ata_host operations are activated together with
> interrupt handler. The conclusion is: interrupt handler may be executed in
> parallel with handlers from ata_port_operations, or, more formally, it may
> interrupt its execution.
> 
> In mv_set_main_irq_mask and in interrupt handler mv_interrupt the interrupt
> mask is modified, but, as I said, handlers from ata_port_operations do not
> acquire any lock. Thus, the interrupt mask may be set incorrectly if the are
> two conflicting modifications.

It depends on which operations.  Most are only called from EH context
and racing there isn't likely to cause any actual issues.  Care to
submit a patch to fix the issue?

Thanks.

-- 
tejun