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SubjectRe: [RFC PATCH 3/8] kmod - teach call_usermodehelper() to use a namespace
On 02/05, Ian Kent wrote:
>
> +int umh_enter_ns(struct task_struct *tsk, struct cred *new)
> +{
> + char path[NS_PATH_MAX];
> + struct vfsmount *mnt;
> + const char *name;
> + pid_t pid;
> + int err = 0;
> +
> + pid = task_pid_nr(tsk);
> +
> + /*
> + * The user mode thread runner runs in the root init namespace
> + * so it will see all system pids.
> + */
> + mnt = task_active_pid_ns(current)->proc_mnt;
> +
> + for (name = ns_names[0]; *name; name++) {
> + struct file *this;
> + int len;
> +
> + len = snprintf(path,
> + NS_PATH_MAX, NS_PATH_FMT,
> + (unsigned long) pid, name);
> + if (len >= NS_PATH_MAX) {
> + err = -ENAMETOOLONG;
> + break;
> + }
> +
> + this = file_open_root(mnt->mnt_root, mnt, path, O_RDONLY);
> + if (unlikely(IS_ERR(this))) {
> + err = PTR_ERR(this);
> + break;
> + }
> +
> + err = setns_inode(file_inode(this), 0);
> + fput(this);
> + if (err)
> + break;
> + }
> +
> + return err;
> +}

Yes, I need to actually read this series and setns paths, but at first glance
there must be a simpler method to call ops->install's and switch_task_namespaces.

Sorry if this was already discussed before, but to me it looks a bit strange
to abuse /proc/ files for this. And again, iiuc file_open_root() can fail if
tsk has already exited (init can be multithreaded).

Oleg.



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