exfat: add a check for invalid data size

Add a check for invalid data size to avoid corrupted filesystem
from being further corrupted.

Signed-off-by: Yuezhang Mo <Yuezhang.Mo@sony.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

Author: YuezhangMo

fs/exfat/namei.c

@@ -646,6 +646,11 @@ static int exfat_find(struct inode *dir, struct qstr *qname,
 	info->valid_size = le64_to_cpu(ep2->dentry.stream.valid_size);
 	info->size = le64_to_cpu(ep2->dentry.stream.size);
 
+	if (unlikely(EXFAT_B_TO_CLU_ROUND_UP(info->size, sbi) > sbi->used_clusters)) {
+		exfat_fs_error(sb, "data size is invalid(%lld)", info->size);
+		return -EIO;
+	}
+
 	info->start_clu = le32_to_cpu(ep2->dentry.stream.start_clu);
 	if (!is_valid_cluster(sbi, info->start_clu) && info->size) {
 		exfat_warn(sb, "start_clu is invalid cluster(0x%x)",