Implemented a first pass of lcall system call prevention.v_2_4_20_6

2 files changed, 20 insertions, 0 deletions

diff --git a/arch/um/kernel/tt/process_kern.c b/arch/um/kernel/tt/process_kern.c
index f858fb8..4cb1406 100644
--- a/arch/um/kernel/tt/process_kern.c
+++ b/arch/um/kernel/tt/process_kern.c
@@ -182,6 +182,7 @@ static void finish_fork_handler(int sig)
 int fork_tramp(void *stack)
 {
 	cli();
+	arch_init_thread();
 	init_new_thread_stack(stack, finish_fork_handler);
 	os_usr1_process(os_getpid());
 	return(0);
diff --git a/arch/um/sys-i386/bugs.c b/arch/um/sys-i386/bugs.c
index 15d0c9f..63d9dbc 100644
--- a/arch/um/sys-i386/bugs.c
+++ b/arch/um/sys-i386/bugs.c
@@ -105,6 +105,25 @@ static int check_cpu_feature(char *feature, int *have_it)
 	return(1);
 }
 
+static void disable_lcall(void)
+{
+	struct modify_ldt_ldt_s ldt;
+	int err;
+
+	bzero(&ldt, sizeof(ldt));
+	ldt.entry_number = 7;
+	ldt.base_addr = 0;
+	ldt.limit = 0;
+	err = modify_ldt(1, &ldt, sizeof(ldt));
+	if(err)
+		printk("Failed to disable lcall7 - errno = %d\n", errno);
+}
+
+void arch_init_thread(void)
+{
+	disable_lcall();
+}
+
 void arch_check_bugs(void)
 {
 	int have_it;