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From: Dan Carpenter <error27@gmail.com>
To: Jan Kara <jack@suse.cz>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>,
	Hannes Eder <hannes@hanneseder.net>,
	Akinobu Mita <akinobu.mita@gmail.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: [patch] udf: potential integer overflow
Date: Mon, 15 Mar 2010 08:21:13 +0000	[thread overview]
Message-ID: <20100315082113.GC18181@bicker> (raw)

bloc->logicalBlockNum is unsigned so it's never less than zero.

When I saw that, it made me worry that "bloc->logicalBlockNum + count"
could overflow.  That's why I changed the check for less than zero
to an overflow check.  (The test works because "count" is also 
unsigned.)

Signed-off-by: Dan Carpenter <error27@gmail.com>
---
GCC 4.1 apparently optimizes overflow checks like this away, but it should
work for other versions of gcc.  I tested with GCC 4.3.
http://www.fefe.de/intof.html

diff --git a/fs/udf/balloc.c b/fs/udf/balloc.c
index 19626e2..9a9378b 100644
--- a/fs/udf/balloc.c
+++ b/fs/udf/balloc.c
@@ -125,9 +125,8 @@ static void udf_bitmap_free_blocks(struct super_block *sb,
 
 	mutex_lock(&sbi->s_alloc_mutex);
 	partmap = &sbi->s_partmaps[bloc->partitionReferenceNum];
-	if (bloc->logicalBlockNum < 0 ||
-	    (bloc->logicalBlockNum + count) >
-		partmap->s_partition_len) {
+	if (bloc->logicalBlockNum + count < count ||
+	    (bloc->logicalBlockNum + count) > partmap->s_partition_len) {
 		udf_debug("%d < %d || %d + %d > %d\n",
 			  bloc->logicalBlockNum, 0, bloc->logicalBlockNum,
 			  count, partmap->s_partition_len);
@@ -393,9 +392,8 @@ static void udf_table_free_blocks(struct super_block *sb,
 
 	mutex_lock(&sbi->s_alloc_mutex);
 	partmap = &sbi->s_partmaps[bloc->partitionReferenceNum];
-	if (bloc->logicalBlockNum < 0 ||
-	    (bloc->logicalBlockNum + count) >
-		partmap->s_partition_len) {
+	if (bloc->logicalBlockNum + count < count ||
+	    (bloc->logicalBlockNum + count) > partmap->s_partition_len) {
 		udf_debug("%d < %d || %d + %d > %d\n",
 			  bloc->logicalBlockNum, 0, bloc->logicalBlockNum, count,
 			  partmap->s_partition_len);

WARNING: multiple messages have this Message-ID (diff)
From: Dan Carpenter <error27@gmail.com>
To: Jan Kara <jack@suse.cz>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>,
	Hannes Eder <hannes@hanneseder.net>,
	Akinobu Mita <akinobu.mita@gmail.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: [patch] udf: potential integer overflow
Date: Mon, 15 Mar 2010 11:21:13 +0300	[thread overview]
Message-ID: <20100315082113.GC18181@bicker> (raw)

bloc->logicalBlockNum is unsigned so it's never less than zero.

When I saw that, it made me worry that "bloc->logicalBlockNum + count"
could overflow.  That's why I changed the check for less than zero
to an overflow check.  (The test works because "count" is also 
unsigned.)

Signed-off-by: Dan Carpenter <error27@gmail.com>
---
GCC 4.1 apparently optimizes overflow checks like this away, but it should
work for other versions of gcc.  I tested with GCC 4.3.
http://www.fefe.de/intof.html

diff --git a/fs/udf/balloc.c b/fs/udf/balloc.c
index 19626e2..9a9378b 100644
--- a/fs/udf/balloc.c
+++ b/fs/udf/balloc.c
@@ -125,9 +125,8 @@ static void udf_bitmap_free_blocks(struct super_block *sb,
 
 	mutex_lock(&sbi->s_alloc_mutex);
 	partmap = &sbi->s_partmaps[bloc->partitionReferenceNum];
-	if (bloc->logicalBlockNum < 0 ||
-	    (bloc->logicalBlockNum + count) >
-		partmap->s_partition_len) {
+	if (bloc->logicalBlockNum + count < count ||
+	    (bloc->logicalBlockNum + count) > partmap->s_partition_len) {
 		udf_debug("%d < %d || %d + %d > %d\n",
 			  bloc->logicalBlockNum, 0, bloc->logicalBlockNum,
 			  count, partmap->s_partition_len);
@@ -393,9 +392,8 @@ static void udf_table_free_blocks(struct super_block *sb,
 
 	mutex_lock(&sbi->s_alloc_mutex);
 	partmap = &sbi->s_partmaps[bloc->partitionReferenceNum];
-	if (bloc->logicalBlockNum < 0 ||
-	    (bloc->logicalBlockNum + count) >
-		partmap->s_partition_len) {
+	if (bloc->logicalBlockNum + count < count ||
+	    (bloc->logicalBlockNum + count) > partmap->s_partition_len) {
 		udf_debug("%d < %d || %d + %d > %d\n",
 			  bloc->logicalBlockNum, 0, bloc->logicalBlockNum, count,
 			  partmap->s_partition_len);

             reply	other threads:[~2010-03-15  8:21 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-03-15  8:21 Dan Carpenter [this message]
2010-03-15  8:21 ` [patch] udf: potential integer overflow Dan Carpenter
2010-03-15 12:08 ` Jan Kara
2010-03-15 12:08   ` Jan Kara

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