state: backend_bucket_circular: fix old state reads

This ports the following barebox commit:

| commit a0c26429e472a175ac6b1736c8687a19a76e97a9
| Author: Philipp Zabel <p.zabel@pengutronix.de>
| Date:   Tue Jul 18 15:14:45 2017 +0200
|
|     state: backend_bucket_circular: fix old state reads
|
|     When the circular bucket meta magic was not found, it is assumed that
|     the whole written state is in the old on-storage format. In that case,
|     the size of the circular bucket meta must not be subtracted from the
|     read length, or the (complete_len > len) check in the raw backend's
|     verify function will fail:
|
|         state: Error, invalid data_len 16 in header, have data of len 24
|
|     Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
|     Signed-off-by: Lucas Stach <l.stach@pengutronix.de>

Signed-off-by: Ulrich Ölmann <u.oelmann@pengutronix.de>
Signed-off-by: Roland Hieber <rhi@pengutronix.de>

1 files changed, 4 insertions, 1 deletions

diff --git a/src/barebox-state/backend_bucket_circular.c b/src/barebox-state/backend_bucket_circular.c
index ec16df2..dd609aa 100644
--- a/src/barebox-state/backend_bucket_circular.c
+++ b/src/barebox-state/backend_bucket_circular.c
@@ -280,7 +280,10 @@ static int state_backend_bucket_circular_read(struct state_backend_storage_bucke
 	}
 
 	*buf_out = buf;
-	*len_out = read_len - sizeof(struct state_backend_storage_bucket_circular_meta);
+	/* When reading old state there is no circular bucket metadata */
+	if (circ->last_written_length)
+		read_len -= sizeof(struct state_backend_storage_bucket_circular_meta);
+	*len_out = read_len;
 
 	return ret;
 }