Re: [PATCH 1/2] common: state: Add property to protect existing data

[Daniel Schultz <d.schultz@phytec.de>]

Hi,

just wanted to remind you to these patches.

Daniel


On 12/14/2017 04:51 PM, Daniel Schultz wrote:
> 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>
> ---
>   .../devicetree/bindings/barebox/barebox,state.rst     |  3 +++
>   common/state/backend_bucket_direct.c                  |  2 ++
>   common/state/backend_storage.c                        |  1 +
>   common/state/state.c                                  | 19 ++++++++++++++++++-
>   common/state/state.h                                  |  2 ++
>   5 files changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/devicetree/bindings/barebox/barebox,state.rst b/Documentation/devicetree/bindings/barebox/barebox,state.rst
> index cebb5f8..db5b041 100644
> --- a/Documentation/devicetree/bindings/barebox/barebox,state.rst
> +++ b/Documentation/devicetree/bindings/barebox/barebox,state.rst
> @@ -55,6 +55,9 @@ Optional Properties
>   * ``algo``: A HMAC algorithm used to detect manipulation of the data
>     or header, sensible values follow this pattern ``hmac(<HASH>)``,
>     e.g. ``hmac(sha256)``. Only available for the ``backend-type`` ``raw``.
> +* ``keep-previous-content``: Check if a the bucket meta magic field contains
> +  other data than the magic value. If so, the backend will not write the state
> +  to prevent unconditionally overwrites of existing data.
>   
>   .. note:: For the ``backend-storage-type`` the keyword ``noncircular`` is still
>      supported as a fall back to an old storage format. Recommendation is to not
> diff --git a/common/state/backend_bucket_direct.c b/common/state/backend_bucket_direct.c
> index 958696e..9d6a337 100644
> --- a/common/state/backend_bucket_direct.c
> +++ b/common/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;
>   		if (!IS_ENABLED(CONFIG_STATE_BACKWARD_COMPATIBLE)) {
>   			dev_err(direct->dev, "No meta data header found\n");
>   			dev_dbg(direct->dev, "Enable backward compatibility or increase stride size\n");
> diff --git a/common/state/backend_storage.c b/common/state/backend_storage.c
> index c6ebe86..f0a169d 100644
> --- a/common/state/backend_storage.c
> +++ b/common/state/backend_storage.c
> @@ -152,6 +152,7 @@ int state_storage_read(struct state_backend_storage *storage,
>   	 * one we want to use.
>   	 */
>   	list_for_each_entry(bucket, &storage->buckets, bucket_list) {
> +		bucket->wrong_magic = 0;
>   		ret = bucket->read(bucket, &bucket->buf, &bucket->len);
>   		if (ret == -EUCLEAN)
>   			bucket->needs_refresh = 1;
> diff --git a/common/state/state.c b/common/state/state.c
> index 6399bd3..e110542 100644
> --- a/common/state/state.c
> +++ b/common/state/state.c
> @@ -44,6 +44,9 @@ int state_save(struct state *state)
>   	void *buf;
>   	ssize_t len;
>   	int ret;
> +	struct state_backend_storage_bucket *bucket;
> +	struct state_backend_storage *storage;
> +	bool has_content;
>   
>   	if (!state->dirty)
>   		return 0;
> @@ -55,7 +58,18 @@ int state_save(struct state *state)
>   		return ret;
>   	}
>   
> -	ret = state_storage_write(&state->storage, buf, len);
> +	storage = &state->storage;
> +	if (state->keep_prev_content) {
> +		has_content = 0;
> +		list_for_each_entry(bucket, &storage->buckets, bucket_list)
> +			has_content |= bucket->wrong_magic;
> +		if (has_content) {
> +			dev_dbg(&state->dev, "Found content on a backend.\n");
> +			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;
> @@ -605,6 +619,9 @@ struct state *state_new_from_node(struct device_node *node, char *path,
>   		}
>   	}
>   
> +	state->keep_prev_content = of_property_read_bool(node,
> +							"keep-previous-content");
> +
>   	state->backend_path = xstrdup(path);
>   
>   	ret = of_property_read_string(node, "backend-type", &backend_type);
> diff --git a/common/state/state.h b/common/state/state.h
> index fcc6b9f..a411b96 100644
> --- a/common/state/state.h
> +++ b/common/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 */
>   	unsigned int dirty;

-- 
Mit freundlichen Grüßen,
With best regards,
   Daniel Schultz

- Entwicklung -
Tel.: 	+49 6131 92 21 457
d.schultz@phytec.de
www.phytec.de

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