[RFC PATCH v3 07/11] KEYS: trusted: TEE: Synchronize session lifetime

[Jarkko Sakkinen <jarkko@kernel.org>]

While the sysfs bind attributes are now suppressed, the parent TEE device
can still remove the device while the instances keep trusted.ko loaded.

Update the static calls before invoking backend init() and reset them in
the case of a failure.

In the TEE backend, guard session context state with a mutex, publish
pvt_data.dev before registering key_type_trusted and sanitize pvt_data on
probe failure and removal.

When an active TEE has not been bound, reject seal, unseal and get_random
with -ENODEV.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
 security/keys/trusted-keys/trusted_core.c | 15 ++--
 security/keys/trusted-keys/trusted_tee.c  | 86 +++++++++++++++++------
 2 files changed, 75 insertions(+), 26 deletions(-)

diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c
index 0509d9955f2a..11d7d296d063 100644
--- a/security/keys/trusted-keys/trusted_core.c
+++ b/security/keys/trusted-keys/trusted_core.c
@@ -373,14 +373,19 @@ static int __init init_trusted(void)
 		if (!get_random)
 			get_random = kernel_get_random;
 
+		static_call_update(trusted_key_seal, trusted_key_sources[i].ops->seal);
+		static_call_update(trusted_key_unseal, trusted_key_sources[i].ops->unseal);
+		static_call_update(trusted_key_get_random, get_random);
+		migratable = trusted_key_sources[i].ops->migratable;
+
 		ret = trusted_key_sources[i].ops->init();
 		if (!ret) {
-			static_call_update(trusted_key_seal, trusted_key_sources[i].ops->seal);
-			static_call_update(trusted_key_unseal, trusted_key_sources[i].ops->unseal);
-			static_call_update(trusted_key_get_random, get_random);
-
 			trusted_key_exit = trusted_key_sources[i].ops->exit;
-			migratable = trusted_key_sources[i].ops->migratable;
+		} else {
+			static_call_update(trusted_key_seal, NULL);
+			static_call_update(trusted_key_unseal, NULL);
+			static_call_update(trusted_key_get_random, NULL);
+			migratable = 0;
 		}
 
 		if (!ret || ret != -ENODEV)
diff --git a/security/keys/trusted-keys/trusted_tee.c b/security/keys/trusted-keys/trusted_tee.c
index 227efb668aa9..87ea549f7f0b 100644
--- a/security/keys/trusted-keys/trusted_tee.c
+++ b/security/keys/trusted-keys/trusted_tee.c
@@ -9,6 +9,7 @@
 #include <linux/err.h>
 #include <linux/key-type.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/tee_drv.h>
@@ -56,6 +57,8 @@ struct trusted_key_tee_private {
 };
 
 static struct trusted_key_tee_private pvt_data;
+/* Do not hold this mutex across key type registration or unregistration. */
+static DEFINE_MUTEX(trusted_key_tee_mutex);
 
 /*
  * Have the TEE seal(encrypt) the symmetric key
@@ -67,6 +70,12 @@ static int trusted_tee_seal(struct trusted_key_payload *p, char *datablob)
 	struct tee_param param[4];
 	struct tee_shm *reg_shm = NULL;
 
+	mutex_lock(&trusted_key_tee_mutex);
+	if (!pvt_data.ctx) {
+		ret = -ENODEV;
+		goto out_unlock;
+	}
+
 	memset(&inv_arg, 0, sizeof(inv_arg));
 	memset(&param, 0, sizeof(param));
 
@@ -74,7 +83,8 @@ static int trusted_tee_seal(struct trusted_key_payload *p, char *datablob)
 					      sizeof(p->key) + sizeof(p->blob));
 	if (IS_ERR(reg_shm)) {
 		dev_err(pvt_data.dev, "shm register failed\n");
-		return PTR_ERR(reg_shm);
+		ret = PTR_ERR(reg_shm);
+		goto out_unlock;
 	}
 
 	inv_arg.func = TA_CMD_SEAL;
@@ -100,7 +110,8 @@ static int trusted_tee_seal(struct trusted_key_payload *p, char *datablob)
 	}
 
 	tee_shm_free(reg_shm);
-
+out_unlock:
+	mutex_unlock(&trusted_key_tee_mutex);
 	return ret;
 }
 
@@ -114,6 +125,12 @@ static int trusted_tee_unseal(struct trusted_key_payload *p, char *datablob)
 	struct tee_param param[4];
 	struct tee_shm *reg_shm = NULL;
 
+	mutex_lock(&trusted_key_tee_mutex);
+	if (!pvt_data.ctx) {
+		ret = -ENODEV;
+		goto out_unlock;
+	}
+
 	memset(&inv_arg, 0, sizeof(inv_arg));
 	memset(&param, 0, sizeof(param));
 
@@ -121,7 +138,8 @@ static int trusted_tee_unseal(struct trusted_key_payload *p, char *datablob)
 					      sizeof(p->key) + sizeof(p->blob));
 	if (IS_ERR(reg_shm)) {
 		dev_err(pvt_data.dev, "shm register failed\n");
-		return PTR_ERR(reg_shm);
+		ret = PTR_ERR(reg_shm);
+		goto out_unlock;
 	}
 
 	inv_arg.func = TA_CMD_UNSEAL;
@@ -147,7 +165,8 @@ static int trusted_tee_unseal(struct trusted_key_payload *p, char *datablob)
 	}
 
 	tee_shm_free(reg_shm);
-
+out_unlock:
+	mutex_unlock(&trusted_key_tee_mutex);
 	return ret;
 }
 
@@ -161,13 +180,20 @@ static int trusted_tee_get_random(unsigned char *key, size_t key_len)
 	struct tee_param param[4];
 	struct tee_shm *reg_shm = NULL;
 
+	mutex_lock(&trusted_key_tee_mutex);
+	if (!pvt_data.ctx) {
+		ret = -ENODEV;
+		goto out_unlock;
+	}
+
 	memset(&inv_arg, 0, sizeof(inv_arg));
 	memset(&param, 0, sizeof(param));
 
 	reg_shm = tee_shm_register_kernel_buf(pvt_data.ctx, key, key_len);
 	if (IS_ERR(reg_shm)) {
 		dev_err(pvt_data.dev, "key shm register failed\n");
-		return PTR_ERR(reg_shm);
+		ret = PTR_ERR(reg_shm);
+		goto out_unlock;
 	}
 
 	inv_arg.func = TA_CMD_GET_RANDOM;
@@ -189,7 +215,8 @@ static int trusted_tee_get_random(unsigned char *key, size_t key_len)
 	}
 
 	tee_shm_free(reg_shm);
-
+out_unlock:
+	mutex_unlock(&trusted_key_tee_mutex);
 	return ret;
 }
 
@@ -205,50 +232,67 @@ static int optee_ctx_match(struct tee_ioctl_version_data *ver, const void *data)
 static int trusted_key_probe(struct tee_client_device *rng_device)
 {
 	struct device *dev = &rng_device->dev;
+	struct tee_context *ctx;
 	int ret;
 	struct tee_ioctl_open_session_arg sess_arg;
 
+	mutex_lock(&trusted_key_tee_mutex);
+	if (pvt_data.ctx) {
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+
 	memset(&sess_arg, 0, sizeof(sess_arg));
 
-	pvt_data.ctx = tee_client_open_context(NULL, optee_ctx_match, NULL,
-					       NULL);
-	if (IS_ERR(pvt_data.ctx))
-		return -ENODEV;
+	ctx = tee_client_open_context(NULL, optee_ctx_match, NULL, NULL);
+	if (IS_ERR(ctx)) {
+		ret = -ENODEV;
+		goto out_unlock;
+	}
 
 	memcpy(sess_arg.uuid, rng_device->id.uuid.b, TEE_IOCTL_UUID_LEN);
 	sess_arg.clnt_login = TEE_IOCTL_LOGIN_REE_KERNEL;
 	sess_arg.num_params = 0;
 
-	ret = tee_client_open_session(pvt_data.ctx, &sess_arg, NULL);
+	ret = tee_client_open_session(ctx, &sess_arg, NULL);
 	if ((ret < 0) || (sess_arg.ret != 0)) {
 		dev_err(dev, "tee_client_open_session failed, err: %x\n",
 			sess_arg.ret);
 		ret = -EINVAL;
 		goto out_ctx;
 	}
+	pvt_data.ctx = ctx;
 	pvt_data.session_id = sess_arg.session;
-
-	ret = register_key_type(&key_type_trusted);
-	if (ret < 0)
-		goto out_sess;
-
 	pvt_data.dev = dev;
+	mutex_unlock(&trusted_key_tee_mutex);
 
-	return 0;
+	ret = register_key_type(&key_type_trusted);
+	if (!ret)
+		return 0;
 
-out_sess:
-	tee_client_close_session(pvt_data.ctx, pvt_data.session_id);
+	mutex_lock(&trusted_key_tee_mutex);
+	tee_client_close_session(ctx, pvt_data.session_id);
 out_ctx:
-	tee_client_close_context(pvt_data.ctx);
-
+	tee_client_close_context(ctx);
+	pvt_data.ctx = NULL;
+	pvt_data.dev = NULL;
+	pvt_data.session_id = 0;
+out_unlock:
+	mutex_unlock(&trusted_key_tee_mutex);
 	return ret;
 }
 
 static void trusted_key_remove(struct tee_client_device *dev)
 {
 	unregister_key_type(&key_type_trusted);
+
+	mutex_lock(&trusted_key_tee_mutex);
 	tee_client_close_session(pvt_data.ctx, pvt_data.session_id);
 	tee_client_close_context(pvt_data.ctx);
+	pvt_data.ctx = NULL;
+	pvt_data.dev = NULL;
+	pvt_data.session_id = 0;
+	mutex_unlock(&trusted_key_tee_mutex);
 }
 
 static const struct tee_client_device_id trusted_key_id_table[] = {
-- 
2.47.3