From 67ac0dde6e51dcf6d5436de61fc13af6960ac313 Mon Sep 17 00:00:00 2001
From: Christian Helmuth <christian.helmuth@genode-labs.com>
Date: Tue, 14 Mar 2017 13:19:02 +0100
Subject: [PATCH] libc: checks for initialization and user context

We check if the libc (kernel singleton, config) was initialized and also
if suspend() is called from the valid user context.

Issue #2332
---
 repos/libports/src/lib/libc/task.cc       | 30 +++++++++++++++--------
 repos/libports/src/lib/libc/vfs_plugin.cc |  4 +++
 2 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/repos/libports/src/lib/libc/task.cc b/repos/libports/src/lib/libc/task.cc
index acf551db53..6052e7cfee 100644
--- a/repos/libports/src/lib/libc/task.cc
+++ b/repos/libports/src/lib/libc/task.cc
@@ -524,6 +524,13 @@ struct Libc::Kernel
 		unsigned long _suspend_main(Suspend_functor &check,
 		                            unsigned long timeout_ms)
 		{
+			/* check if we're running on the user context */
+			if (Thread::myself()->mystack().top != (Genode::addr_t)_user_stack) {
+				error("libc suspend() called from non-user context (",
+				      __builtin_return_address(0), ") - aborting");
+				exit(1);
+			}
+
 			if (!check.suspend())
 				return 0;
 
@@ -774,9 +781,12 @@ static void resumed_callback() { kernel->entrypoint_resumed(); }
 void Libc::resume_all() { kernel->resume_all(); }
 
 
-unsigned long Libc::suspend(Suspend_functor &s,
-                             unsigned long timeout_ms)
+unsigned long Libc::suspend(Suspend_functor &s, unsigned long timeout_ms)
 {
+	if (!kernel) {
+		error("libc kernel not initialized, needed for suspend()");
+		exit(1);
+	}
 	return kernel->suspend(s, timeout_ms);
 }
 
@@ -789,8 +799,8 @@ unsigned long Libc::current_time()
 void Libc::schedule_suspend(void (*suspended) ())
 {
 	if (!kernel) {
-		error("libc kernel not initialized, needed for suspend()");
-		return;
+		error("libc kernel not initialized, needed for fork()");
+		exit(1);
 	}
 	kernel->schedule_suspend(suspended);
 }
@@ -800,7 +810,7 @@ void Libc::schedule_select(Libc::Select_handler_base *h)
 {
 	if (!kernel) {
 		error("libc kernel not initialized, needed for select()");
-		return;
+		exit(1);
 	}
 	kernel->schedule_select(h);
 }
@@ -813,6 +823,11 @@ void Libc::execute_in_application_context(Libc::Application_code &app_code)
 	 *     don't use this code.
 	 */
 
+	if (!kernel) {
+		error("libc kernel not initialized, needed for with_libc()");
+		exit(1);
+	}
+
 	static bool nested = false;
 
 	if (nested) {
@@ -825,11 +840,6 @@ void Libc::execute_in_application_context(Libc::Application_code &app_code)
 		return;
 	}
 
-	if (!kernel) {
-		error("libc kernel not initialized, needed for with_libc()");
-		return;
-	}
-
 	nested = true;
 	kernel->run(app_code);
 	nested = false;
diff --git a/repos/libports/src/lib/libc/vfs_plugin.cc b/repos/libports/src/lib/libc/vfs_plugin.cc
index a63409b23e..9a3377c096 100644
--- a/repos/libports/src/lib/libc/vfs_plugin.cc
+++ b/repos/libports/src/lib/libc/vfs_plugin.cc
@@ -91,6 +91,10 @@ namespace Libc {
 	Genode::Xml_node config() __attribute__((weak));
 	Genode::Xml_node config()
 	{
+		if (!_config_node) {
+			error("libc config not initialized - aborting");
+			exit(1);
+		}
 		return *_config_node;
 	}