state: Add property to protect existing data

This ports the following barebox commit:

| commit 67c1c0853fa06bcbc1725e93b6ad9942e80a1e56
| Author: Daniel Schultz <d.schultz@phytec.de>
| Date:   Thu Apr 12 11:13:01 2018 +0200
|
|     common: state: Add property to protect existing data
|
|     After an update to a newer barebox version with an enabled state
|     framework, existing data in storage memories could be overwritten.
|
|     Add a new property to check in front of every write task, if the meta
|     magic field only contains the magic number, zeros or ones.
|
|     Signed-off-by: Daniel Schultz <d.schultz@phytec.de>
|     Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

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

4 files changed, 27 insertions, 4 deletions

diff --git a/src/barebox-state/backend_bucket_circular.c b/src/barebox-state/backend_bucket_circular.c
index 2a0e34d..ec78748 100644
--- a/src/barebox-state/backend_bucket_circular.c
+++ b/src/barebox-state/backend_bucket_circular.c
@@ -397,11 +397,13 @@ static int state_backend_bucket_circular_init(
 			meta = (struct state_backend_storage_bucket_circular_meta *)
 					(buf + sub_offset + circ->writesize - sizeof(*meta));
 
-			if (meta->magic != circular_magic)
+			if (meta->magic != circular_magic) {
 				written_length = 0;
-			else
+				if (meta->magic != ~0 && !!meta->magic)
+					bucket->wrong_magic = 1;
+			} else {
 				written_length = meta->written_length;
-
+			}
 			break;
 		}
 	}
diff --git a/src/barebox-state/backend_bucket_direct.c b/src/barebox-state/backend_bucket_direct.c
index 4465ed0..dc00de0 100644
--- a/src/barebox-state/backend_bucket_direct.c
+++ b/src/barebox-state/backend_bucket_direct.c
@@ -69,6 +69,8 @@ static int state_backend_bucket_direct_read(struct state_backend_storage_bucket
 	if (meta.magic == direct_magic) {
 		read_len = meta.written_length;
 	} else {
+		if (meta.magic != ~0 && !!meta.magic)
+			bucket->wrong_magic = 1;
 		read_len = direct->max_size;
 		ret = lseek(direct->fd, direct->offset, SEEK_SET);
 		if (ret < 0) {
diff --git a/src/barebox-state/state.c b/src/barebox-state/state.c
index 0ec5664..eb2b3eb 100644
--- a/src/barebox-state/state.c
+++ b/src/barebox-state/state.c
@@ -43,6 +43,8 @@ int state_save(struct state *state)
 	void *buf;
 	ssize_t len;
 	int ret;
+	struct state_backend_storage_bucket *bucket;
+	struct state_backend_storage *storage;
 
 	if (!state->dirty)
 		return 0;
@@ -54,7 +56,19 @@ int state_save(struct state *state)
 		return ret;
 	}
 
-	ret = state_storage_write(&state->storage, buf, len);
+	storage = &state->storage;
+	if (state->keep_prev_content) {
+		bool has_content = 0;
+		list_for_each_entry(bucket, &storage->buckets, bucket_list)
+			has_content |= bucket->wrong_magic;
+		if (has_content) {
+			dev_err(&state->dev, "Found foreign content on backend, won't overwrite.\n");
+			ret = -EPERM;
+			goto out;
+		}
+	}
+
+	ret = state_storage_write(storage, buf, len);
 	if (ret) {
 		dev_err(&state->dev, "Failed to write packed state, %d\n", ret);
 		goto out;
@@ -628,6 +642,9 @@ struct state *state_new_from_node(struct device_node *node, bool readonly)
 
 	of_property_read_string(node, "backend-storage-type", &storage_type);
 
+	state->keep_prev_content = of_property_read_bool(node,
+							"keep-previous-content");
+
 	ret = state_format_init(state, backend_type, node, alias);
 	if (ret)
 		goto out_release_state;
diff --git a/src/barebox-state/state.h b/src/barebox-state/state.h
index 6670523..3a0662f 100644
--- a/src/barebox-state/state.h
+++ b/src/barebox-state/state.h
@@ -46,6 +46,7 @@ struct state_backend_storage_bucket {
 	void *buf;
 	ssize_t len;
 	bool needs_refresh;
+	bool wrong_magic;
 };
 
 /**
@@ -105,6 +106,7 @@ struct state {
 	char *of_path;
 	const char *name;
 	uint32_t magic;
+	bool keep_prev_content;
 
 	struct list_head variables; /* Sorted list of variables */