linux-kernel - [PATCH 1/2] Eliminate double kfree

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Date:	Thu, 29 May 2008 15:04:38 +0200 (CEST)
From:	Julia Lawall <julia@...u.dk>
To:	jbarnes@...tuousgeek.org, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH 1/2] Eliminate double kfree

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

The destination of goto error also does a kfree(g_iommus), so it is not
correct to do one here.

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

// <smpl>
@r1@
expression E;
position p1,p2;
@@

kfree@p1(E);
...
kfree@p2(E);

@subexps@
expression E1;
position r1.p1,p;
@@

kfree@p1(<+... E1@p ...+>);

@recollect@
position subexps.p;
expression E1;
@@

E1@p

@doublekfree@
position r1.p1,r1.p2;
expression recollect.E1,E2,E;
position p;
statement S;
@@

kfree@p1(E);
<+... E1@...2 ...+> // the actual semantic match contains other assignments
kfree@p2(E);

@notdoublekfree@
position r1.p1,r1.p2;
position any doublekfree.p;
expression E,E1,E2;
@@

* kfree@p1(E);
... when != E1@p
    when != E1@p = E2 // needed to match a variable decl
* kfree@p2(E);
// </smpl>

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

diff -u -p a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
--- a/drivers/pci/intel-iommu.c	2008-05-15 18:11:35.000000000 +0200
+++ b/drivers/pci/intel-iommu.c	2008-05-24 21:20:24.000000000 +0200
@@ -1725,7 +1725,6 @@ int __init init_dmars(void)
 	deferred_flush = kzalloc(g_num_of_iommus *
 		sizeof(struct deferred_flush_tables), GFP_KERNEL);
 	if (!deferred_flush) {
-		kfree(g_iommus);
 		ret = -ENOMEM;
 		goto error;
 	}
--
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