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

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Date:	Sat, 26 Nov 2011 10:44:17 +0600
From:	Rakib Mullick <rakib.mullick@...il.com>
To:	Keith Packard <keithp@...thp.com>
Cc:	Daniel Vetter <daniel@...ll.ch>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Subject: Re: [PATCH] drm, i915: Fix memory leak in i915_gem_busy_ioctl().

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.

Index: work/modi.linux-3.1.1/drivers/gpu/drm/i915/i915_gem.c
===================================================================
--- work.orig/modi.linux-3.1.1/drivers/gpu/drm/i915/i915_gem.c
+++ work/modi.linux-3.1.1/drivers/gpu/drm/i915/i915_gem.c
@@ -1736,8 +1736,6 @@ i915_add_request(struct intel_ring_buffe
 	int was_empty;
 	int ret;

-	BUG_ON(request == NULL);
-
 	ret = ring->add_request(ring, &seqno);
 	if (ret)
 	    return ret;
@@ -2002,9 +2000,11 @@ i915_gem_retire_work_handler(struct work
 			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);
+			if (request) {
+				ret = i915_add_request(ring, NULL, request);
+				if (ret)
+					kfree(request);
+			}
 		}

 		idle &= list_empty(&ring->request_list);


Thanks,
Rakib
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