linux-kernel - Re: [PATCH] drm, i915: Fix memory leak in i915_gem_busy

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Message-ID: <CADZ9YHinT6Y98Ks6Zs3UnG2xQSJYqDN5W1RgrNtyaPz-n8Zajg@mail.gmail.com>
Date:	Sat, 26 Nov 2011 22:29:12 +0600
From:	Rakib Mullick <rakib.mullick@...il.com>
To:	Chris Wilson <chris@...is-wilson.co.uk>
Cc:	Keith Packard <keithp@...thp.com>, akpm@...ux-foundation.org,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm, i915: Fix memory leak in i915_gem_busy_ioctl().

On Sat, Nov 26, 2011 at 4:57 PM, Chris Wilson <chris@...is-wilson.co.uk> wrote:
> On Sat, 26 Nov 2011 10:44:17 +0600, Rakib Mullick <rakib.mullick@...il.com> wrote:
>> On Mon, Nov 21, 2011 at 11:16 PM, Keith Packard <keithp@...thp.com> wrote:
>> > On Mon, 21 Nov 2011 17:23:06 +0100, Daniel Vetter <daniel@...ll.ch> wrote:
>> >
>> >> Indeed, nice catch (albeit totally unlikely to be hit, because the error
>> >> only happens when the gpu ceases to progress in the ring, so imo not
>> >> stable material). Keith, please pick this up for fixes, thanks.
>> >
>> > It's already there and queued for airlied :-)
>> >
>> Thank you guys for reviewing and taking the patch.
>>
>> Now, while I was looking at the uses of i915_add_request(), I found
>> the following code :
>>
>>                         ret = i915_gem_flush_ring(ring, 0,
>> I915_GEM_GPU_DOMAINS);
>>                         request = kzalloc(sizeof(*request), GFP_KERNEL);
>>                         if (ret || request == NULL ||
>>                             i915_add_request(ring, NULL, request))
>>                             kfree(request);
>>
>> From above code, we might ended up by calling kfree(request) without
>> allocating request. Though, it's unlikely cause if request is NULL
>> then BUG_ON will be hit in i915_add_request(). So, to unify the callee
>> uses of i915_add_request(), I'm proposing the following patch. Please
>> let me know what do you guys think. If you guys agree, I can sent a
>> formal patch.
>
> kfree(NULL) is permitted and taken advantage of here along with the
> short-circuiting behaviour of '||'.

Yes, no real problem with current code. I was just thinking from code
cleanup's pov. Is BUG_ON really needed in i915_add_request() ?

thanks,
Rakib
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