seccomp: extract check/assign mode helpers

To support splitting mode 1 from mode 2, extract the mode checking and
assignment logic into common functions.

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Andy Lutomirski <luto@amacapital.net>

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index afb916c..9df7def 100644 (file)
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -194,7 +194,23 @@ static u32 seccomp_run_filters(int syscall)
        }
        return ret;
 }
+#endif /* CONFIG_SECCOMP_FILTER */
 
+static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode)
+{
+       if (current->seccomp.mode && current->seccomp.mode != seccomp_mode)
+               return false;
+
+       return true;
+}
+
+static inline void seccomp_assign_mode(unsigned long seccomp_mode)
+{
+       current->seccomp.mode = seccomp_mode;
+       set_tsk_thread_flag(current, TIF_SECCOMP);
+}
+
+#ifdef CONFIG_SECCOMP_FILTER
 /**
  * seccomp_attach_filter: Attaches a seccomp filter to current.
  * @fprog: BPF program to install
@@ -490,8 +506,7 @@ static long seccomp_set_mode(unsigned long seccomp_mode, char __user *filter)
 {
        long ret = -EINVAL;
 
-       if (current->seccomp.mode &&
-           current->seccomp.mode != seccomp_mode)
+       if (!seccomp_may_assign_mode(seccomp_mode))
                goto out;
 
        switch (seccomp_mode) {
@@ -512,8 +527,7 @@ static long seccomp_set_mode(unsigned long seccomp_mode, char __user *filter)
                goto out;
        }
 
-       current->seccomp.mode = seccomp_mode;
-       set_thread_flag(TIF_SECCOMP);
+       seccomp_assign_mode(seccomp_mode);
 out:
        return ret;
 }