linux-kernel - Re: A potential race in drivers/staging/speakup/speakup.ko

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Date:   Mon, 5 Sep 2016 13:33:33 +0300
From:   Pavel Andrianov <andrianov@...ras.ru>
To:     Samuel Thibault <samuel.thibault@...-lyon.org>,
        William Hubbs <w.d.hubbs@...il.com>,
        Chris Brannon <chris@...-brannons.com>,
        Kirk Reiser <kirk@...sers.ca>, speakup@...ux-speakup.org,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        Vaishali Thakkar <vaishali.thakkar@...cle.com>,
        ldv-project@...uxtesting.org
Subject: Re: A potential race in drivers/staging/speakup/speakup.ko

05.09.2016 12:56, Samuel Thibault пишет:
> Pavel Andrianov, on Mon 05 Sep 2016 12:54:10 +0300, wrote:
>> 05.09.2016 12:43, Samuel Thibault пишет:
>>> Pavel Andrianov, on Mon 05 Sep 2016 11:51:50 +0300, wrote:
>>>> There is a potential race in drivers/staging/speakup/speakup.ko.
>>>> All operations with global pointers buff_in and buff_out are performed
>>>> without any locks. Thus, a simultaneous write (via synth_buffer_clear or
>>>> synth_buffer_add) to the pointers may lead to inconsistent data.
>>>>
>>>> Should a local lock be used here?
>>>
>>> AIUI, all callers of these functions have speakup_info.spinlock held.
>>
>> Regard a call stack
>>
>> -> synth_direct_store
>>   -> synth_printf
>>     -> synth_buffer_add
>>
>> The functions have not held speakup_info.spinlock.
>
> Apparently there is currently no caller of synth_direct_store and
> synth_store. But taking the lock here would be needed indeed.
>
> Samuel
>

synth_direct_store may be called via device_attributes interface. In 
which function the lock should be added?

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