[PATCHv7 1/7] nvmem: Add flag to export NVMEM to root only

Andrew Lunn
2016-02-26T20:01:15Z

Legacy AT24, AT25 EEPROMs are exported in sys so that only root can
read the contents. The EEPROMs may contain sensitive information. Add
a flag so the provide can indicate that NVMEM should also restrict
access to root only.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
---
drivers/nvmem/core.c | 57 ++++++++++++++++++++++++++++++++++++++++--
include/linux/nvmem-provider.h | 1 +
2 files changed, 56 insertions(+), 2 deletions(-)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index de14fae6f7f6..b03690bc8f09 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -161,6 +161,53 @@ static const struct attribute_group *nvmem_ro_dev_groups[] = {
NULL,
};

+/* default read/write permissions, root only */
+static struct bin_attribute bin_attr_rw_root_nvmem = {
+ .attr = {
+ .name = "nvmem",
+ .mode = S_IWUSR | S_IRUSR,
+ },
+ .read = bin_attr_nvmem_read,
+ .write = bin_attr_nvmem_write,
+};
+
+static struct bin_attribute *nvmem_bin_rw_root_attributes[] = {
+ &bin_attr_rw_root_nvmem,
+ NULL,
+};
+
+static const struct attribute_group nvmem_bin_rw_root_group = {
+ .bin_attrs = nvmem_bin_rw_root_attributes,
+};
+
+static const struct attribute_group *nvmem_rw_root_dev_groups[] = {
+ &nvmem_bin_rw_root_group,
+ NULL,
+};
+
+/* read only permission, root only */
+static struct bin_attribute bin_attr_ro_root_nvmem = {
+ .attr = {
+ .name = "nvmem",
+ .mode = S_IRUSR,
+ },
+ .read = bin_attr_nvmem_read,
+};
+
+static struct bin_attribute *nvmem_bin_ro_root_attributes[] = {
+ &bin_attr_ro_root_nvmem,
+ NULL,
+};
+
+static const struct attribute_group nvmem_bin_ro_root_group = {
+ .bin_attrs = nvmem_bin_ro_root_attributes,
+};
+
+static const struct attribute_group *nvmem_ro_root_dev_groups[] = {
+ &nvmem_bin_ro_root_group,
+ NULL,
+};
+
static void nvmem_release(struct device *dev)
{
struct nvmem_device *nvmem = to_nvmem_device(dev);
@@ -355,8 +402,14 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
nvmem->read_only = of_property_read_bool(np, "read-only") |
config->read_only;

- nvmem->dev.groups = nvmem->read_only ? nvmem_ro_dev_groups :
- nvmem_rw_dev_groups;
+ if (config->root_only)
+ nvmem->dev.groups = nvmem->read_only ?
+ nvmem_ro_root_dev_groups :
+ nvmem_rw_root_dev_groups;
+ else
+ nvmem->dev.groups = nvmem->read_only ?
+ nvmem_ro_dev_groups :
+ nvmem_rw_dev_groups;

device_initialize(&nvmem->dev);

diff --git a/include/linux/nvmem-provider.h b/include/linux/nvmem-provider.h
index 0b68caff1b3c..d24fefa0c11d 100644
--- a/include/linux/nvmem-provider.h
+++ b/include/linux/nvmem-provider.h
@@ -23,6 +23,7 @@ struct nvmem_config {
const struct nvmem_cell_info *cells;
int ncells;
bool read_only;
+ bool root_only;
};

#if IS_ENABLED(CONFIG_NVMEM)
--
2.7.0