linux-kernel - Re: [PATCH v2 1/5] HID: intel_ish-hid: fix potential uninitialized data usage

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Date:   Mon, 22 May 2017 23:33:58 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:     Jiri Kosina <jikos@...nel.org>, linux-input@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/5] HID: intel_ish-hid: fix potential uninitialized
 data usage

On Mon, May 22, 2017 at 9:17 PM, Srinivas Pandruvada
<srinivas.pandruvada@...ux.intel.com> wrote:
> Hi Arnd,
> On Thu, 2017-05-18 at 22:21 +0200, Arnd Bergmann wrote:
>> gcc points out an uninialized pointer dereference that could happen
>> if we ever get to recv_ishtp_cl_msg_dma() or recv_ishtp_cl_msg()
>> with an empty &dev->read_list:
>>
>> drivers/hid/intel-ish-hid/ishtp/client.c: In function
>> 'recv_ishtp_cl_msg_dma':
>> drivers/hid/intel-ish-hid/ishtp/client.c:1049:3: error: 'cl' may be
>> used uninitialized in this function [-Werror=maybe-uninitialized]
>>
>> The warning only appeared in very few randconfig builds, as the
>> spinlocks tend to prevent gcc from tracing the variables. I only
>> saw it in configurations that had neither SMP nor LOCKDEP enabled.
>>
>> As we can see, we only enter the case if 'complete_rb' is non-NULL,
>> and then 'cl' is known to point to complete_rb->cl. Adding another
>> initialization to the same pointer is harmless here and makes it
>> clear to the compiler that the behavior is well-defined.
>>
> Did you get chance to test these changes on a platform with ISH?

No, I only build-tested it and though about the fix carefully.

        Arnd