On 19/04/2017 00:23, Kees Cook wrote: > On Tue, Mar 28, 2017 at 4:46 PM, Mickaël Salaün <[email protected]> wrote: >> The semantic is unchanged. This will be useful for the Landlock >> integration with seccomp (next commit). >> >> Signed-off-by: Mickaël Salaün <[email protected]> >> Cc: Kees Cook <[email protected]> >> Cc: Andy Lutomirski <[email protected]> >> Cc: Will Drewry <[email protected]> >> --- >> 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.
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