From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Carpenter Date: Mon, 15 Mar 2010 08:21:13 +0000 Subject: [patch] udf: potential integer overflow Message-Id: <20100315082113.GC18181@bicker> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Jan Kara Cc: Pekka Enberg , Hannes Eder , Akinobu Mita , Al Viro , linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org 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 --- 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);