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

[Andy Lutomirski]

On Tue, Jun 24, 2014 at 12:18 PM, Oleg Nesterov <oleg at redhat.com> wrote:
> On 06/23, Kees Cook wrote:
>>
>> --- 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