Re: [PATCH v7 4/9] seccomp: move no_new_privs into seccomp

On Tue, Jun 24, 2014 at 12:18 PM, Oleg Nesterov [off-list ref] wrote:

On 06/23, Kees Cook wrote:

quoted

--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h

@@ -3,6 +3,8 @@

 #include <uapi/linux/seccomp.h>

+#define SECCOMP_FLAG_NO_NEW_PRIVS    0       /* task may not gain privs */
+
 #ifdef CONFIG_SECCOMP

 #include <linux/thread_info.h>

@@ -16,6 +18,7 @@ struct seccomp_filter;
  *         system calls available to a process.
  * @filter: must always point to a valid seccomp-filter or NULL as it is
  *          accessed without locking during system call entry.
+ * @flags: flags under task->sighand->siglock lock
  *
  *          @filter must only be accessed from the context of current as there
  *          is no read locking.

@@ -23,6 +26,7 @@ struct seccomp_filter;
 struct seccomp {
      int mode;
      struct seccomp_filter *filter;
+     unsigned long flags;
 };

 extern int __secure_computing(int);

@@ -51,7 +55,9 @@ static inline int seccomp_mode(struct seccomp *s)

 #include <linux/errno.h>

-struct seccomp { };
+struct seccomp {
+     unsigned long flags;
+};

A bit messy ;)

I am wondering if we can simply do

        static inline bool current_no_new_privs(void)
        {
                if (current->no_new_privs)
                        return true;

        #ifdef CONFIG_SECCOMP
                if (test_thread_flag(TIF_SECCOMP))
                        return true;
        #endif

Nope -- privileged users can enable seccomp w/o nnp.

--Andy