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

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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

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Thread

[PATCHv7 0/7] Convert exiting EEPROM drivers to NVMEM Andrew Lunn <andrew@lunn.ch> - 2016-02-26 21:00 +0100
  [PATCHv7 3/7] eeprom: at24: extend driver to plug into the NVMEM framework Andrew Lunn <andrew@lunn.ch> - 2016-02-26 21:00 +0100
    Re: [PATCHv7 3/7] eeprom: at24: extend driver to plug into the NVMEM  framework Vladimir Zapolskiy <vz@mleia.com> - 2016-03-02 22:50 +0100
      Re: [PATCHv7 3/7] eeprom: at24: extend driver to plug into the NVMEM  framework Andrew Lunn <andrew@lunn.ch> - 2016-03-02 22:50 +0100
        Re: [PATCHv7 3/7] eeprom: at24: extend driver to plug into the NVMEM  framework Vladimir Zapolskiy <vz@mleia.com> - 2016-03-03 00:10 +0100
  [PATCHv7 5/7] eeprom: at25: extend driver to plug into the NVMEM framework Andrew Lunn <andrew@lunn.ch> - 2016-02-26 21:10 +0100
    Re: [PATCHv7 5/7] eeprom: at25: extend driver to plug into the NVMEM  framework Vladimir Zapolskiy <vz@mleia.com> - 2016-03-02 23:00 +0100
  [PATCHv7 4/7] eeprom: at25: Remove in kernel API for accessing the EEPROM Andrew Lunn <andrew@lunn.ch> - 2016-02-26 21:10 +0100
    Re: [PATCHv7 4/7] eeprom: at25: Remove in kernel API for accessing  the EEPROM Wolfram Sang <wsa@the-dreams.de> - 2016-02-28 22:10 +0100
  [PATCHv7 6/7] eeprom: 93xx46: extend driver to plug into the NVMEM framework Andrew Lunn <andrew@lunn.ch> - 2016-02-26 21:10 +0100
    Re: [PATCHv7 6/7] eeprom: 93xx46: extend driver to plug into the  NVMEM framework Vladimir Zapolskiy <vz@mleia.com> - 2016-03-02 23:10 +0100
      Re: [PATCHv7 6/7] eeprom: 93xx46: extend driver to plug into the  NVMEM framework Andrew Lunn <andrew@lunn.ch> - 2016-03-02 23:30 +0100
        Re: [PATCHv7 6/7] eeprom: 93xx46: extend driver to plug into the  NVMEM framework Vladimir Zapolskiy <vz@mleia.com> - 2016-03-03 00:20 +0100
  [PATCHv7 7/7] misc: at24: replace memory_accessor with nvmem_device_read Andrew Lunn <andrew@lunn.ch> - 2016-02-26 21:10 +0100
    Re: [PATCHv7 7/7] misc: at24: replace memory_accessor with  nvmem_device_read Wolfram Sang <wsa@the-dreams.de> - 2016-02-28 22:10 +0100
  [PATCHv7 1/7] nvmem: Add flag to export NVMEM to root only Andrew Lunn <andrew@lunn.ch> - 2016-02-26 21:10 +0100
  [PATCHv7 2/7] nvmem: Add backwards compatibility support for older EEPROM drivers. Andrew Lunn <andrew@lunn.ch> - 2016-02-26 21:10 +0100
  Re: [PATCHv7 0/7] Convert exiting EEPROM drivers to NVMEM Greg KH <gregkh@linuxfoundation.org> - 2016-03-02 02:00 +0100

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