Merge tag 'amdtee-fix-for-v6.6' of https://git.linaro.org/people/jens.wiklander/linux-tee into arm/fixes

AMDTEE fix possible use-after-free

* tag 'amdtee-fix-for-v6.6' of https://git.linaro.org/people/jens.wiklander/linux-tee:
  tee: amdtee: fix use-after-free vulnerability in amdtee_close_session

Link: https://lore.kernel.org/r/20231003171835.GA669924@rayden
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Author: arndb

drivers/tee/amdtee/core.c

@@ -217,12 +217,12 @@ static int copy_ta_binary(struct tee_context *ctx, void *ptr, void **ta,
 	return rc;
 }
 
+/* mutex must be held by caller */
 static void destroy_session(struct kref *ref)
 {
 	struct amdtee_session *sess = container_of(ref, struct amdtee_session,
 						   refcount);
 
-	mutex_lock(&session_list_mutex);
 	list_del(&sess->list_node);
 	mutex_unlock(&session_list_mutex);
 	kfree(sess);
@@ -272,7 +272,8 @@ int amdtee_open_session(struct tee_context *ctx,
 	if (arg->ret != TEEC_SUCCESS) {
 		pr_err("open_session failed %d\n", arg->ret);
 		handle_unload_ta(ta_handle);
-		kref_put(&sess->refcount, destroy_session);
+		kref_put_mutex(&sess->refcount, destroy_session,
+			       &session_list_mutex);
 		goto out;
 	}
 
@@ -290,7 +291,8 @@ int amdtee_open_session(struct tee_context *ctx,
 		pr_err("reached maximum session count %d\n", TEE_NUM_SESSIONS);
 		handle_close_session(ta_handle, session_info);
 		handle_unload_ta(ta_handle);
-		kref_put(&sess->refcount, destroy_session);
+		kref_put_mutex(&sess->refcount, destroy_session,
+			       &session_list_mutex);
 		rc = -ENOMEM;
 		goto out;
 	}
@@ -331,7 +333,7 @@ int amdtee_close_session(struct tee_context *ctx, u32 session)
 	handle_close_session(ta_handle, session_info);
 	handle_unload_ta(ta_handle);
 
-	kref_put(&sess->refcount, destroy_session);
+	kref_put_mutex(&sess->refcount, destroy_session, &session_list_mutex);
 
 	return 0;
 }