hfsplus: fix overflow in hfsplus_read_wrapper

For partitions larger than 2TB or at such an offset the hfs wrapper code
in hfsplus might overflow the range representable in a 32-bit
data type. Make sure we use a sector_t for the arithmetics leading to it.

I'm not sure this code can be readed at all as hfs itself never supported
such large volumes.
Signed-off-by: Christoph Hellwig <hch@tuxera.com>

fs/hfsplus/wrapper.c

@@ -172,8 +172,9 @@ int hfsplus_read_wrapper(struct super_block *sb)
 		if (!hfsplus_read_mdb(sbi->s_vhdr, &wd))
 			goto out_free_backup_vhdr;
 		wd.ablk_size >>= HFSPLUS_SECTOR_SHIFT;
-		part_start += wd.ablk_start + wd.embed_start * wd.ablk_size;
-		part_size = wd.embed_count * wd.ablk_size;
+		part_start += (sector_t)wd.ablk_start +
+			       (sector_t)wd.embed_start * wd.ablk_size;
+		part_size = (sector_t)wd.embed_count * wd.ablk_size;
 		goto reread;
 	default:
 		/*