ubi: eba: properly rollback inside self_check_eba

In case of a memory allocation failure in the volumes loop we can only
process the already allocated scan_eba and fm_eba array elements on the
error path - others are still uninitialized.

Found by Linux Verification Center (linuxtesting.org).

Fixes: 00abf304 ("UBI: Add self_check_eba()")
Cc: stable@vger.kernel.org
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

drivers/mtd/ubi/eba.c

@@ -1564,6 +1564,7 @@ int self_check_eba(struct ubi_device *ubi, struct ubi_attach_info *ai_fastmap,
 					  GFP_KERNEL);
 		if (!fm_eba[i]) {
 			ret = -ENOMEM;
+			kfree(scan_eba[i]);
 			goto out_free;
 		}
 
@@ -1599,7 +1600,7 @@ int self_check_eba(struct ubi_device *ubi, struct ubi_attach_info *ai_fastmap,
 	}
 
 out_free:
-	for (i = 0; i < num_volumes; i++) {
+	while (--i >= 0) {
 		if (!ubi->volumes[i])
 			continue;