Hello,
On Tue, Dec 12, 2023 at 01:17:40PM -0800, Kees Cook wrote:
...
> @@ -127,7 +127,7 @@ static struct kernfs_node *kernfs_common_ancestor(struct
> kernfs_node *a,
> *
> * [3] when @kn_to is %NULL result will be "(null)"
> *
> - * Return: the length of the full path. If the full length is equal to or
> + * Return: the length of the constructed path. If the path would have been
> * greater than @buflen, @buf contains the truncated path with the trailing
> * '\0'. On error, -errno is returned.
> */
...
> /* Calculate how many bytes we need for the rest */
We probably should drop this comment.
> for (i = depth_to - 1; i >= 0; i--) {
> for (kn = kn_to, j = 0; j < i; j++)
> kn = kn->parent;
> - len += strlcpy(buf + len, "/",
> - len < buflen ? buflen - len : 0);
> - len += strlcpy(buf + len, kn->name,
> - len < buflen ? buflen - len : 0);
> +
> + len += scnprintf(buf + len, buflen - len, "/%s", kn->name);
scnprintf doesn't return -E2BIG on overflow, right? It just returns the
truncated length, so the overflow behavior would be different depending on
where this function overflows, right? Not a huge problem but it may be
better to keep calling strscpy to keep things consistent?
> --- a/kernel/cgroup/cgroup.c
> +++ b/kernel/cgroup/cgroup.c
> @@ -1893,7 +1893,7 @@ int cgroup_show_path(struct seq_file *sf, struct
> kernfs_node *kf_node,
> len = kernfs_path_from_node(kf_node, ns_cgroup->kn, buf, PATH_MAX);
> spin_unlock_irq(&css_set_lock);
>
> - if (len >= PATH_MAX)
> + if (len == -E2BIG)
> len = -ERANGE;
I'd just pass up -E2BIG.
> else if (len > 0) {
> seq_escape(sf, buf, " \t\n\\");
> @@ -6301,7 +6301,7 @@ int proc_cgroup_show(struct seq_file *m, struct
> pid_namespace *ns,
> if (cgroup_on_dfl(cgrp) || !(tsk->flags & PF_EXITING)) {
> retval = cgroup_path_ns_locked(cgrp, buf, PATH_MAX,
> current->nsproxy->cgroup_ns);
> - if (retval >= PATH_MAX)
> + if (retval == -E2BIG)
> retval = -ENAMETOOLONG;
Ditto.
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 615daaf87f1f..fb29158ae825 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -4941,7 +4941,7 @@ int proc_cpuset_show(struct seq_file *m, struct
> pid_namespace *ns,
> retval = cgroup_path_ns(css->cgroup, buf, PATH_MAX,
> current->nsproxy->cgroup_ns);
> css_put(css);
> - if (retval >= PATH_MAX)
> + if (retval == -E2BIG)
Ditto.
Thanks.
--
tejun
