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

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Message-Id: <e0d58a$2cdsbh@orsmga002.jf.intel.com>
Date:	Sat, 26 Nov 2011 10:57:22 +0000
From:	Chris Wilson <chris@...is-wilson.co.uk>
To:	Rakib Mullick <rakib.mullick@...il.com>,
	Keith Packard <keithp@...thp.com>
Cc:	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, 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 '||'.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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