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udf: potential integer overflow

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From: Linux Kernel Mailing List
Subject: udf: potential integer overflow
Date: Monday, April 12, 2010 - 7:59 pm

Gitweb:     http://git.kernel.org/linus/69ecbbedac8e353bbd924fad16fed0c7c54e6382
Commit:     69ecbbedac8e353bbd924fad16fed0c7c54e6382
Parent:     0fdf86754f70e813845af4abaa805165ce57a0bb
Author:     Dan Carpenter <error27@gmail.com>
AuthorDate: Mon Mar 15 11:21:13 2010 +0300
Committer:  Jan Kara <jack@suse.cz>
CommitDate: Thu Apr 8 15:35:20 2010 +0200

    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>
---
 fs/udf/balloc.c |   10 ++++------
 1 files changed, 4 insertions(+), 6 deletions(-)

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",
 			  ...
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