On Thu, Jan 12, 2012 at 8:50 AM, Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
> On 01/11, Will Drewry wrote:
>>
>> This patch adds support for seccomp mode 2. This mode enables dynamic
>> enforcement of system call filtering policy in the kernel as specified
>> by a userland task. The policy is expressed in terms of a BPF program,
>> as is used for userland-exposed socket filtering. Instead of network
>> data, the BPF program is evaluated over struct user_regs_struct at the
>> time of the system call (as retrieved using regviews).
>
> Cool ;)
>
> I didn't really read this patch yet, just one nit.
>
>> +#define seccomp_filter_init_task(_tsk) do { \
>> + (_tsk)->seccomp.filter = NULL; \
>> +} while (0);
>
> Cosmetic and subjective, but imho it would be better to add inline
> functions instead of define's.
Refactoring it a bit to make that possible. Since seccomp fork/init/free
never needs access to the whole task_structs, I'll just pass in what's
needed (and avoid the sched.h inclusion recursion).
Comments on the next round will most definitely be appreciated!
>> @@ -166,6 +167,7 @@ void free_task(struct task_struct *tsk)
>> free_thread_info(tsk->stack);
>> rt_mutex_debug_task_free(tsk);
>> ftrace_graph_exit_task(tsk);
>> + seccomp_filter_free_task(tsk);
>> free_task_struct(tsk);
>> }
>> EXPORT_SYMBOL(free_task);
>> @@ -1209,6 +1211,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
>> /* Perform scheduler related setup. Assign this task to a CPU. */
>> sched_fork(p);
>>
>> + seccomp_filter_init_task(p);
>
> This doesn't look right or I missed something. something seccomp_filter_init_task()
> should be called right after dup_task_struct(), at least before copy process can
> fail.
>
> Otherwise copy_process()->free_fork()->seccomp_filter_free_task() can put
> current->seccomp.filter copied by arch_dup_task_struct().
Ah - makes sense! I moved it under dup_task_struct before any goto's
to bad_fork_free.
>> +struct seccomp_filter {
>> + struct kref usage;
>> + struct pid *creator;
>
> Why? seccomp_filter->creator is never used, no?
Removing it. It is from a related patch I'm experimenting with (adding
optional tracehook support), but it has no bearing here.
Thanks - new patch revision incoming!
will
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