Re: [PATCH] cgroup/cpuset: Prevent UAF in proc_cpuset_show()

[Markus Elfring]

…
> +++ b/kernel/cgroup/cpuset.c
…
> @@ -5051,10 +5066,12 @@ int proc_cpuset_show(struct seq_file *m, struct pid_namespace *ns,
>  	if (!buf)
>  		goto out;
>
> +	mutex_lock(&cpuset_mutex);
>  	css = task_get_css(tsk, cpuset_cgrp_id);
>  	retval = cgroup_path_ns(css->cgroup, buf, PATH_MAX,
>  				current->nsproxy->cgroup_ns);
>  	css_put(css);
> +	mutex_unlock(&cpuset_mutex);
…

Under which circumstances would you become interested to apply a statement
like “guard(mutex)(&cpuset_mutex);”?
https://elixir.bootlin.com/linux/v6.10-rc4/source/include/linux/mutex.h#L196

Regards,
Markus