linux-kernel - Re: [PATCH] HID: multitouch: prevent memleak with the allocated name

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Message-ID: <CAN+gG=ESjWJDfHN4KmMAnLUko-wCa8r0VzQmFYqDme5Jg+FszA@mail.gmail.com>
Date:	Thu, 30 May 2013 15:21:02 +0200
From:	Benjamin Tissoires <benjamin.tissoires@...il.com>
To:	Andy Shevchenko <andy.shevchenko@...il.com>
Cc:	Benjamin Tissoires <benjamin.tissoires@...hat.com>,
	Henrik Rydberg <rydberg@...omail.se>,
	Jiri Kosina <jkosina@...e.cz>,
	Stephane Chatty <chatty@...c.fr>,
	linux-input <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] HID: multitouch: prevent memleak with the allocated name

Hi Andy,

On Wed, May 29, 2013 at 10:12 PM, Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
> On Wed, May 29, 2013 at 11:45 AM, Benjamin Tissoires
> <benjamin.tissoires@...hat.com> wrote:
>> mt_free_input_name() was never called during .remove():
>> hid_hw_stop() removes the hid_input items in hdev->inputs, and so the
>> list is therefore empty after the call. In the end, we never free the
>> special names that has been allocated during .probe().
>>
>> Restore the original name before freeing it to avoid acessing already
>> freed pointer.
>>
>
>> I just spotted this one yesterday... My guess is that this way is safe (without
>> a locking mechanism to prevent accessing hi->input->name), but I'm not 100% sure.
>
> Hi Jiri, Benjamin.
>
> What do you think about patch I just sent?

Thanks for looking at this. My very first concern is that none of the
HID part has been devm-ized (this is on my todo-if-I-have-some-time
list). The input susbsystem has been devm-ized quite recently, so this
should be possible now.
So, basically, I honestly don't know if using part of devm mallocs in
hid-multitouch is safe and if it will work as expected. Maybe Jiri
will have a better idea.

I have a few comments on your patch if Jiri wants to include it.

>
> P.S. Benjamin, I re-used your commit message, I think you have no objections.

No objections :)

Cheers,
Benjamin
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