fs/ntfs3: Fix a couple integer overflows on 32bit systems

On 32bit systems the "off + sizeof(struct NTFS_DE)" addition can
have an integer wrapping issue.  Fix it by using size_add().

Fixes: 82cae26 ("fs/ntfs3: Add initialization of super block")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

Author: Dan Carpenter

fs/ntfs3/index.c

@@ -618,7 +618,7 @@ static bool index_hdr_check(const struct INDEX_HDR *hdr, u32 bytes)
 	u32 off = le32_to_cpu(hdr->de_off);
 
 	if (!IS_ALIGNED(off, 8) || tot > bytes || end > tot ||
-	    off + sizeof(struct NTFS_DE) > end) {
+	    size_add(off, sizeof(struct NTFS_DE)) > end) {
 		/* incorrect index buffer. */
 		return false;
 	}
@@ -736,7 +736,7 @@ static struct NTFS_DE *hdr_find_e(const struct ntfs_index *indx,
 	if (end > total)
 		return NULL;
 
-	if (off + sizeof(struct NTFS_DE) > end)
+	if (size_add(off, sizeof(struct NTFS_DE)) > end)
 		return NULL;
 
 	e = Add2Ptr(hdr, off);