linux-kernel - [PATCH 8/10] s390/pci: use safer test on the result of find_first_zero

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Date:	Wed,  4 Jun 2014 11:07:58 +0200
From:	Julia Lawall <Julia.Lawall@...6.fr>
To:	Sebastian Ott <sebott@...ux.vnet.ibm.com>
Cc:	kernel-janitors@...r.kernel.org,
	Gerald Schaefer <gerald.schaefer@...ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux390@...ibm.com, linux-s390@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 8/10] s390/pci: use safer test on the result of find_first_zero_bit

From: Julia Lawall <Julia.Lawall@...6.fr>

Find_first_zero_bit considers BITS_PER_LONG bits at a time, and thus may
return a larger number than the maximum position argument if that position
is not a multiple of BITS_PER_LONG.

The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression e1,e2,e3;
statement S1,S2;
@@

e1 = find_first_zero_bit(e2,e3)
...
if (e1 
- ==
+ >=
  e3)
S1 else S2
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@...6.fr>

---
 arch/s390/pci/pci.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff -u -p a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
--- a/arch/s390/pci/pci.c
+++ b/arch/s390/pci/pci.c
@@ -566,7 +566,7 @@ static int zpci_alloc_iomap(struct zpci_
 
 	spin_lock(&zpci_iomap_lock);
 	entry = find_first_zero_bit(zpci_iomap, ZPCI_IOMAP_MAX_ENTRIES);
-	if (entry == ZPCI_IOMAP_MAX_ENTRIES) {
+	if (entry >= ZPCI_IOMAP_MAX_ENTRIES) {
 		spin_unlock(&zpci_iomap_lock);
 		return -ENOSPC;
 	}
@@ -746,7 +746,7 @@ static int zpci_alloc_domain(struct zpci
 {
 	spin_lock(&zpci_domain_lock);
 	zdev->domain = find_first_zero_bit(zpci_domain, ZPCI_NR_DEVICES);
-	if (zdev->domain == ZPCI_NR_DEVICES) {
+	if (zdev->domain >= ZPCI_NR_DEVICES) {
 		spin_unlock(&zpci_domain_lock);
 		return -ENOSPC;
 	}

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