[patch 4/5] [RFC] Add MMC password protection (lock/unlock) support

From: Anderson Briglia
Date: Wed Dec 14 2005 - 08:32:35 EST



Implement MMC password reset and forced erase support. It uses the sysfs
mechanism to send commands to the MMC subsystem. Usage:

Forced erase:

echo erase > /sys/bus/mmc/devices/mmc0\:0001/lockable

Remove password:

echo remove > /sys/bus/mmc/devices/mmc0\:0001/lockable

Signed-off-by: Anderson Briglia <anderson.briglia@xxxxxxxxxxx>
Signed-off-by: Anderson Lizardo <anderson.lizardo@xxxxxxxxxxx>
Signed-off-by: Carlos Eduardo Aguiar <carlos.aguiar@xxxxxxxxxxx>

Index: linux-2.6.14-omap2/drivers/mmc/mmc_sysfs.c
===================================================================
--- linux-2.6.14-omap2.orig/drivers/mmc/mmc_sysfs.c 2005-12-13 17:22:13.000000000 -0400
+++ linux-2.6.14-omap2/drivers/mmc/mmc_sysfs.c 2005-12-13 17:22:14.000000000 -0400
@@ -16,6 +16,7 @@
#include <linux/device.h>
#include <linux/idr.h>
#include <linux/key.h>
+#include <linux/err.h>

#include <linux/mmc/card.h>
#include <linux/mmc/host.h>
@@ -64,6 +65,58 @@ static struct device_attribute mmc_dev_a

static struct device_attribute mmc_dev_attr_scr = MMC_ATTR_RO(scr);

+#ifdef CONFIG_MMC_PASSWORDS
+
+static ssize_t
+mmc_lockable_show(struct device *dev, struct device_attribute *att, char *buf)
+{
+ struct mmc_card *card = dev_to_mmc_card(dev);
+
+ if (!mmc_card_lockable(card))
+ return sprintf(buf, "unlockable\n");
+ else
+ return sprintf(buf, "lockable, %slocked\n", mmc_card_locked(card) ?
+ "" : "un");
+}
+
+/*
+ * implement MMC password reset ("remove password") and forced erase ("forgot
+ * password").
+ */
+static ssize_t
+mmc_lockable_store(struct device *dev, struct device_attribute *att,
+ const char *data, size_t len)
+{
+ struct mmc_card *card = dev_to_mmc_card(dev);
+
+ if (!mmc_card_lockable(card))
+ return -EINVAL;
+
+ if (mmc_card_locked(card) && !strncmp(data, "erase", 5)) {
+ /* forced erase only works while card is locked */
+ mmc_lock_unlock(card, NULL, MMC_LOCK_MODE_ERASE);
+ return len;
+ } else if (!mmc_card_locked(card) && !strncmp(data, "remove", 6)) {
+ /* remove password only works while card is unlocked */
+ struct key *mmc_key = request_key(&mmc_key_type, "mmc:key", NULL);
+
+ if (!IS_ERR(mmc_key)) {
+ int err = mmc_lock_unlock(card, mmc_key, MMC_LOCK_MODE_CLR_PWD);
+ if (!err)
+ return len;
+ } else
+ dev_dbg(&card->dev, "request_key returned error %ld\n", PTR_ERR(mmc_key));
+ }
+
+ return -EINVAL;
+}
+
+static struct device_attribute mmc_dev_attr_lockable =
+ __ATTR(lockable, S_IWUSR | S_IRUGO,
+ mmc_lockable_show, mmc_lockable_store);
+
+#endif
+

static void mmc_release_card(struct device *dev)
{
@@ -235,6 +288,13 @@ int mmc_register_card(struct mmc_card *c
if (ret)
device_del(&card->dev);
}
+#ifdef CONFIG_MMC_PASSWORDS
+ if (mmc_card_lockable(card)) {
+ ret = device_create_file(&card->dev, &mmc_dev_attr_lockable);
+ if (ret)
+ device_del(&card->dev);
+ }
+#endif
}
return ret;
}
@@ -248,7 +308,10 @@ void mmc_remove_card(struct mmc_card *ca
if (mmc_card_present(card)) {
if (mmc_card_sd(card))
device_remove_file(&card->dev, &mmc_dev_attr_scr);
-
+#ifdef CONFIG_MMC_PASSWORDS
+ if (mmc_card_lockable(card))
+ device_remove_file(&card->dev, &mmc_dev_attr_lockable);
+#endif
device_del(&card->dev);
}


--
Anderson Briglia,
Anderson Lizardo,
Carlos Eduardo Aguiar

Embedded Linux Lab - 10LE
Nokia Institute of Technology - INdT
Manaus - Brazil