On Thu, Apr 12, 2018 at 11:13:01AM +0200, 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@xxxxxxxxx>
> ---
> Changes:
> v2: Added check for circular backend
> Improved error message if content was found
>
Applied, thanks
Sascha
> .../devicetree/bindings/barebox/barebox,state.rst | 3 +++
> common/state/backend_bucket_circular.c | 8 +++++---
> common/state/backend_bucket_direct.c | 2 ++
> common/state/state.c | 19 ++++++++++++++++++-
> common/state/state.h | 2 ++
> 5 files changed, 30 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/barebox/barebox,state.rst b/Documentation/devicetree/bindings/barebox/barebox,state.rst
> index 872bac0..2893937 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_circular.c b/common/state/backend_bucket_circular.c
> index 2324903..933493e 100644
> --- a/common/state/backend_bucket_circular.c
> +++ b/common/state/backend_bucket_circular.c
> @@ -396,11 +396,13 @@ 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/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/state.c b/common/state/state.c
> index 73dfb58..25d9502 100644
> --- a/common/state/state.c
> +++ b/common/state/state.c
> @@ -44,6 +44,8 @@ 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;
> @@ -55,7 +57,19 @@ 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;
> @@ -623,6 +637,9 @@ 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/common/state/state.h b/common/state/state.h
> index 6670523..3a0662f 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 */
>
> --
> 2.7.4
>
>
> _______________________________________________
> barebox mailing list
> barebox@xxxxxxxxxxxxxxxxxxx
> http://lists.infradead.org/mailman/listinfo/barebox
>
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