linux-kernel - [PATCH] drivers/video/pnx4008: eliminate double free

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Date:	Sun, 27 Apr 2008 12:46:22 +0200 (CEST)
From:	Julia Lawall <julia@...u.dk>
To:	adaplas@...il.com, linux-fbdev-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] drivers/video/pnx4008: eliminate double free

From: Julia Lawall <julia@...u.dk>

The function framebuffer_release just calls kfree, so calling kfree
subsequently on the same argument represents a double free.  The
comments with the definition of framebuffer_release
in drivers/video/fbsysfs.c suggest that a more elaborate definition of this
function is planned, such that the splitting up of framebuffer_release and
kfree as done in the second instance might someday make sense, but it does
not make sense now. 

This was found using the following semantic match.
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@@
expression E;
@@

* kfree(E);
...
* framebuffer_release(E);

@@
expression E;
@@

* framebuffer_release(E);
...
* kfree(E);
// </smpl>

Signed-off-by: Julia Lawall <julia@...u.dk>
---

diff -u -p a/drivers/video/pnx4008/pnxrgbfb.c b/drivers/video/pnx4008/pnxrgbfb.c
--- a/drivers/video/pnx4008/pnxrgbfb.c	2008-04-07 13:50:27.000000000 +0200
+++ b/drivers/video/pnx4008/pnxrgbfb.c	2008-04-27 12:25:52.000000000 +0200
@@ -100,7 +100,6 @@ static int rgbfb_remove(struct platform_
 		fb_dealloc_cmap(&info->cmap);
 		framebuffer_release(info);
 		platform_set_drvdata(pdev, NULL);
-		kfree(info);
 	}
 
 	pnx4008_free_dum_channel(channel_owned, pdev->id);
@@ -168,23 +167,21 @@ static int __devinit rgbfb_probe(struct 
 
 	ret = fb_alloc_cmap(&info->cmap, 256, 0);
 	if (ret < 0)
-		goto err2;
+		goto err1;
 
 	ret = register_framebuffer(info);
 	if (ret < 0)
-		goto err3;
+		goto err2;
 	platform_set_drvdata(pdev, info);
 
 	return 0;
 
-err3:
-	fb_dealloc_cmap(&info->cmap);
 err2:
-	framebuffer_release(info);
+	fb_dealloc_cmap(&info->cmap);
 err1:
 	pnx4008_free_dum_channel(channel_owned, pdev->id);
 err0:
-	kfree(info);
+	framebuffer_release(info);
 err:
 	return ret;
 }
--
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