1 files changed, 86 insertions, 0 deletions
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
new file mode 100644
index 0000000..57d4b13
--- /dev/null
+++ b/kernel/seccomp.c
@@ -0,0 +1,86 @@
+/*
+ * linux/kernel/seccomp.c
+ *
+ * Copyright 2004-2005  Andrea Arcangeli <andrea@cpushare.com>
+ *
+ * This defines a simple but solid secure-computing mode.
+ */
+
+#include <linux/seccomp.h>
+#include <linux/sched.h>
+#include <linux/compat.h>
+
+/* #define SECCOMP_DEBUG 1 */
+#define NR_SECCOMP_MODES 1
+
+/*
+ * Secure computing mode 1 allows only read/write/exit/sigreturn.
+ * To be fully secure this must be combined with rlimit
+ * to limit the stack allocations too.
+ */
+static int mode1_syscalls[] = {
+	__NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
+	0, /* null terminated */
+};
+
+#ifdef CONFIG_COMPAT
+static int mode1_syscalls_32[] = {
+	__NR_seccomp_read_32, __NR_seccomp_write_32, __NR_seccomp_exit_32, __NR_seccomp_sigreturn_32,
+	0, /* null terminated */
+};
+#endif
+
+void __secure_computing(int this_syscall)
+{
+	int mode = current->seccomp.mode;
+	int * syscall;
+
+	switch (mode) {
+	case 1:
+		syscall = mode1_syscalls;
+#ifdef CONFIG_COMPAT
+		if (is_compat_task())
+			syscall = mode1_syscalls_32;
+#endif
+		do {
+			if (*syscall == this_syscall)
+				return;
+		} while (*++syscall);
+		break;
+	default:
+		BUG();
+	}
+
+#ifdef SECCOMP_DEBUG
+	dump_stack();
+#endif
+	do_exit(SIGKILL);
+}
+
+long prctl_get_seccomp(void)
+{
+	return current->seccomp.mode;
+}
+
+long prctl_set_seccomp(unsigned long seccomp_mode)
+{
+	long ret;
+
+	/* can set it only once to be even more secure */
+	ret = -EPERM;
+	if (unlikely(current->seccomp.mode))
+		goto out;
+
+	ret = -EINVAL;
+	if (seccomp_mode && seccomp_mode <= NR_SECCOMP_MODES) {
+		current->seccomp.mode = seccomp_mode;
+		set_thread_flag(TIF_SECCOMP);
+#ifdef TIF_NOTSC
+		disable_TSC();
+#endif
+		ret = 0;
+	}
+
+ out:
+	return ret;
+}