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>

1 files changed, 18 insertions, 4 deletions

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index afb916c7e890..9df7def86c3b 100644
--- 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;
 }