Patchwork [net-next,v6,05/11] seccomp: Split put_seccomp_filter() with put_seccomp()

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Submitter Mickaël Salaün
Date March 28, 2017, 11:46 p.m.
Message ID <20170328234650.19695-6-mic@digikod.net>
Download mbox | patch
Permalink /patch/9650673/
State New
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Comments

Mickaël Salaün - March 28, 2017, 11:46 p.m.
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(-)
Kees Cook - April 18, 2017, 10:23 p.m.
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?

> +
>  /*
>   * 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.

-Kees
Mickaël Salaün - April 18, 2017, 10:47 p.m.
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.
Mickaël Salaün - April 19, 2017, 10:18 p.m.
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?
Kees Cook - April 20, 2017, 1:54 a.m.
On Wed, Apr 19, 2017 at 3:18 PM, Mickaël Salaün <mic@digikod.net> wrote:
>
> 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?

Sure! Though I still think the argument to get/put_seccomp_filter()
should be task_struct.

-Kees

Patch

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);
+
 /*
  * 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;
 
 out: