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Potential race condition in drivers/ata/sata_mv.ko

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  Potential race condition in drivers/ata/sata_mv.ko Pavel Andrianov <andrianov@ispras.ru> - 2016-08-05 14:50 +0200
    Re: Potential race condition in drivers/ata/sata_mv.ko Tejun Heo <tj@kernel.org> - 2016-08-10 06:00 +0200

#1457079 — Potential race condition in drivers/ata/sata_mv.ko

Hi!

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.


-- 
Pavel Andrianov
Linux Verification Center, ISPRAS
web: http://linuxtesting.org
e-mail: andrianov@ispras.ru

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#1459274

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

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