acpi/nfit, libnvdimm: Add enable/update passphrase support for Intel nvdimms

Add support for enabling and updating passphrase on the Intel nvdimms.
The passphrase is the an encrypted key in the kernel user keyring.
We trigger the update via writing "update <old_keyid> <new_keyid>" to the
sysfs attribute "security". If no <old_keyid> exists (for enabling
security) then a 0 should be used.
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/nvdimm/dimm_devs.c

@@ -392,8 +392,9 @@ static ssize_t security_show(struct device *dev,
 }
 
 #define OPS						\
-	C( OP_FREEZE,        "freeze",        1),	\
-	C( OP_DISABLE,       "disable",       2)
+	C( OP_FREEZE,		"freeze",	1),	\
+	C( OP_DISABLE,		"disable",	2),	\
+	C( OP_UPDATE,		"update",	3)
 #undef C
 #define C(a, b, c) a
 enum nvdimmsec_op_ids { OPS };
@@ -444,6 +445,9 @@ static ssize_t __security_store(struct device *dev, const char *buf, size_t len)
 	} else if (i == OP_DISABLE) {
 		dev_dbg(dev, "disable %u\n", key);
 		rc = nvdimm_security_disable(nvdimm, key);
+	} else if (i == OP_UPDATE) {
+		dev_dbg(dev, "update %u %u\n", key, newkey);
+		rc = nvdimm_security_update(nvdimm, key, newkey);
 	} else
 		return -EINVAL;
 
@@ -493,7 +497,8 @@ static umode_t nvdimm_visible(struct kobject *kobj, struct attribute *a, int n)
 	if (nvdimm->sec.state < 0)
 		return 0;
 	/* Are there any state mutation ops? */
-	if (nvdimm->sec.ops->freeze || nvdimm->sec.ops->disable)
+	if (nvdimm->sec.ops->freeze || nvdimm->sec.ops->disable
+			|| nvdimm->sec.ops->change_key)
 		return a->mode;
 	return 0444;
 }

drivers/nvdimm/nd-core.h

@@ -59,12 +59,19 @@ static inline enum nvdimm_security_state nvdimm_security_state(
 int nvdimm_security_freeze(struct nvdimm *nvdimm);
 #if IS_ENABLED(CONFIG_NVDIMM_KEYS)
 int nvdimm_security_disable(struct nvdimm *nvdimm, unsigned int keyid);
+int nvdimm_security_update(struct nvdimm *nvdimm, unsigned int keyid,
+		unsigned int new_keyid);
 #else
 static inline int nvdimm_security_disable(struct nvdimm *nvdimm,
 		unsigned int keyid)
 {
 	return -EOPNOTSUPP;
 }
+static inline int nvdimm_security_update(struct nvdimm *nvdimm, unsigned int keyid,
+		unsigned int new_keyid)
+{
+	return -EOPNOTSUPP;
+}
 #endif
 
 /**

drivers/nvdimm/security.c

@@ -15,6 +15,9 @@
 #include "nd-core.h"
 #include "nd.h"
 
+#define NVDIMM_BASE_KEY		0
+#define NVDIMM_NEW_KEY		1
+
 static bool key_revalidate = true;
 module_param(key_revalidate, bool, 0444);
 MODULE_PARM_DESC(key_revalidate, "Require key validation at init.");
@@ -70,7 +73,7 @@ static struct key *nvdimm_request_key(struct nvdimm *nvdimm)
 }
 
 static struct key *nvdimm_lookup_user_key(struct nvdimm *nvdimm,
-		key_serial_t id)
+		key_serial_t id, int subclass)
 {
 	key_ref_t keyref;
 	struct key *key;
@@ -86,10 +89,10 @@ static struct key *nvdimm_lookup_user_key(struct nvdimm *nvdimm,
 		key_put(key);
 		return NULL;
 	}
-	dev_dbg(dev, "%s: key found: %#x\n", __func__, key_serial(key));
 
+	dev_dbg(dev, "%s: key found: %#x\n", __func__, key_serial(key));
 
-	down_read(&key->sem);
+	down_read_nested(&key->sem, subclass);
 	epayload = dereference_key_locked(key);
 	if (epayload->decrypted_datalen != NVDIMM_PASSPHRASE_LEN) {
 		up_read(&key->sem);
@@ -197,7 +200,7 @@ int nvdimm_security_disable(struct nvdimm *nvdimm, unsigned int keyid)
 		return -EIO;
 	}
 
-	key = nvdimm_lookup_user_key(nvdimm, keyid);
+	key = nvdimm_lookup_user_key(nvdimm, keyid, NVDIMM_BASE_KEY);
 	if (!key)
 		return -ENOKEY;
 
@@ -209,3 +212,50 @@ int nvdimm_security_disable(struct nvdimm *nvdimm, unsigned int keyid)
 	nvdimm->sec.state = nvdimm_security_state(nvdimm);
 	return rc;
 }
+
+int nvdimm_security_update(struct nvdimm *nvdimm, unsigned int keyid,
+		unsigned int new_keyid)
+{
+	struct device *dev = &nvdimm->dev;
+	struct nvdimm_bus *nvdimm_bus = walk_to_nvdimm_bus(dev);
+	struct key *key, *newkey;
+	int rc;
+
+	/* The bus lock should be held at the top level of the call stack */
+	lockdep_assert_held(&nvdimm_bus->reconfig_mutex);
+
+	if (!nvdimm->sec.ops || !nvdimm->sec.ops->change_key
+			|| nvdimm->sec.state < 0)
+		return -EOPNOTSUPP;
+
+	if (nvdimm->sec.state >= NVDIMM_SECURITY_FROZEN) {
+		dev_warn(dev, "Incorrect security state: %d\n",
+				nvdimm->sec.state);
+		return -EIO;
+	}
+
+	if (keyid == 0)
+		key = NULL;
+	else {
+		key = nvdimm_lookup_user_key(nvdimm, keyid, NVDIMM_BASE_KEY);
+		if (!key)
+			return -ENOKEY;
+	}
+
+	newkey = nvdimm_lookup_user_key(nvdimm, new_keyid, NVDIMM_NEW_KEY);
+	if (!newkey) {
+		nvdimm_put_key(key);
+		return -ENOKEY;
+	}
+
+	rc = nvdimm->sec.ops->change_key(nvdimm, key ? key_data(key) : NULL,
+			key_data(newkey));
+	dev_dbg(dev, "key: %d %d update: %s\n",
+			key_serial(key), key_serial(newkey),
+			rc == 0 ? "success" : "fail");
+
+	nvdimm_put_key(newkey);
+	nvdimm_put_key(key);
+	nvdimm->sec.state = nvdimm_security_state(nvdimm);
+	return rc;
+}