On 01/13, Will Drewry wrote:
>
> When prctl(PR_SECCOMP_EXT, SECCOMP_EXT_ACT_TSYNC, 0, 0) is called, it
> will attempt to synchronize all threads in current's threadgroup to its
> seccomp filter program.
TBH, I do not understand what this patch actually does ;) I'll try to
read it later. Still a couple of nits.
> +static pid_t seccomp_sync_threads(void)
> +{
> + struct task_struct *thread, *caller;
> + pid_t failed = 0;
> + thread = caller = current;
> +
> + read_lock(&tasklist_lock);
> + if (thread_group_empty(caller))
> + goto done;
You can check thread_group_empty() before tasklist_lock, otherwise
this fast-path before while_each_thread() makes no sense.
> + while_each_thread(caller, thread) {
> + task_lock(thread);
Could you remind what task_lock() protects wrt seccomp?
> + } else {
> + /* Keep the last sibling that failed to return. */
> + struct pid *pid = get_task_pid(thread, PIDTYPE_PID);
> + failed = pid_vnr(pid);
> + put_pid(pid);
> + /* If the pid cannot be resolved, then return -ESRCH */
> + if (failed == 0)
> + failed = -ESRCH;
You can just do
failed = task_pid_vnr(thread);
"failed == 0" is not possible either way (we are doing while_each_thread
under tasklist, the task can't do detach_pid).
Oleg.
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