On 19/04/2017 00:47, Mickaël Salaün wrote:
> 
> On 19/04/2017 00:23, Kees Cook wrote:
>> On Tue, Mar 28, 2017 at 4:46 PM, Mickaël Salaün <mic@digikod.net> wrote:
>>> The semantic is unchanged. This will be useful for the Landlock
>>> integration with seccomp (next commit).
>>>
>>> Signed-off-by: Mickaël Salaün <mic@digikod.net>
>>> Cc: Kees Cook <keescook@chromium.org>
>>> Cc: Andy Lutomirski <luto@amacapital.net>
>>> Cc: Will Drewry <wad@chromium.org>
>>> ---
>>>  include/linux/seccomp.h |  4 ++--
>>>  kernel/fork.c           |  2 +-
>>>  kernel/seccomp.c        | 18 +++++++++++++-----
>>>  3 files changed, 16 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
>>> index ecc296c137cd..e25aee2cdfc0 100644
>>> --- a/include/linux/seccomp.h
>>> +++ b/include/linux/seccomp.h
>>> @@ -77,10 +77,10 @@ static inline int seccomp_mode(struct seccomp *s)
>>>  #endif /* CONFIG_SECCOMP */
>>>
>>>  #ifdef CONFIG_SECCOMP_FILTER
>>> -extern void put_seccomp_filter(struct task_struct *tsk);
>>> +extern void put_seccomp(struct task_struct *tsk);
>>>  extern void get_seccomp_filter(struct task_struct *tsk);
>>>  #else  /* CONFIG_SECCOMP_FILTER */
>>> -static inline void put_seccomp_filter(struct task_struct *tsk)
>>> +static inline void put_seccomp(struct task_struct *tsk)
>>>  {
>>>         return;
>>>  }
>>> diff --git a/kernel/fork.c b/kernel/fork.c
>>> index 6c463c80e93d..a27d8e67ce33 100644
>>> --- a/kernel/fork.c
>>> +++ b/kernel/fork.c
>>> @@ -363,7 +363,7 @@ void free_task(struct task_struct *tsk)
>>>  #endif
>>>         rt_mutex_debug_task_free(tsk);
>>>         ftrace_graph_exit_task(tsk);
>>> -       put_seccomp_filter(tsk);
>>> +       put_seccomp(tsk);
>>>         arch_release_task_struct(tsk);
>>>         if (tsk->flags & PF_KTHREAD)
>>>                 free_kthread_struct(tsk);
>>> diff --git a/kernel/seccomp.c b/kernel/seccomp.c
>>> index 65f61077ad50..326f79e32127 100644
>>> --- a/kernel/seccomp.c
>>> +++ b/kernel/seccomp.c
>>> @@ -64,6 +64,8 @@ struct seccomp_filter {
>>>  /* Limit any path through the tree to 256KB worth of instructions. */
>>>  #define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
>>>
>>> +static void put_seccomp_filter(struct seccomp_filter *filter);
>>
>> Can this be reorganized easily to avoid a forward-declaration?
> 
> I didn't want to move too much code but I will.
> 
>>
>>> +
>>>  /*
>>>   * Endianness is explicitly ignored and left for BPF program authors to manage
>>>   * as per the specific architecture.
>>> @@ -314,7 +316,7 @@ static inline void seccomp_sync_threads(void)
>>>                  * current's path will hold a reference.  (This also
>>>                  * allows a put before the assignment.)
>>>                  */
>>> -               put_seccomp_filter(thread);
>>> +               put_seccomp_filter(thread->seccomp.filter);
>>>                 smp_store_release(&thread->seccomp.filter,
>>>                                   caller->seccomp.filter);
>>>
>>> @@ -476,10 +478,11 @@ static inline void seccomp_filter_free(struct seccomp_filter *filter)
>>>         }
>>>  }
>>>
>>> -/* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */
>>> -void put_seccomp_filter(struct task_struct *tsk)
>>> +/* put_seccomp_filter - decrements the ref count of a filter */
>>> +static void put_seccomp_filter(struct seccomp_filter *filter)
>>>  {
>>> -       struct seccomp_filter *orig = tsk->seccomp.filter;
>>> +       struct seccomp_filter *orig = filter;
>>> +
>>>         /* Clean up single-reference branches iteratively. */
>>>         while (orig && atomic_dec_and_test(&orig->usage)) {
>>>                 struct seccomp_filter *freeme = orig;
>>> @@ -488,6 +491,11 @@ void put_seccomp_filter(struct task_struct *tsk)
>>>         }
>>>  }
>>>
>>> +void put_seccomp(struct task_struct *tsk)
>>> +{
>>> +       put_seccomp_filter(tsk->seccomp.filter);
>>> +}
>>> +
>>>  static void seccomp_init_siginfo(siginfo_t *info, int syscall, int reason)
>>>  {
>>>         memset(info, 0, sizeof(*info));
>>> @@ -914,7 +922,7 @@ long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
>>>         if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog)))
>>>                 ret = -EFAULT;
>>>
>>> -       put_seccomp_filter(task);
>>> +       put_seccomp_filter(task->seccomp.filter);
>>>         return ret;
>>
>> I don't like that the arguments to get_seccomp_filter() and
>> put_seccomp_filter() are now different. I think they should match for
>> readability.
> 
> OK, I can do that.
> 

Kees, can I send this as a separate patch?