udf: potential integer overflow

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>
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/udf/balloc.c b/fs/udf/balloc.c
index 19626e2491c4656b56fe672d3a9f3f8a09143c66..9a9378b4eb5ae2c89495b9025d7be8c5aa04ef5b 100644 (file)
--- 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);