On Fri, Dec 08, 2023 at 10:33:09AM +0100, Max Kellermann wrote:
> By passing the fsugid to kernfs_create_dir_ns(), we don't need
> cgroup_kn_set_ugid() any longer. That function was added for exactly
> this purpose by commit 49957f8e2a43 ("cgroup: newly created dirs and
> files should be owned by the creator").
>
> Eliminating this piece of duplicate code means we benefit from future
> improvements to kernfs_create_dir_ns(); for example, both are lacking
> S_ISGID support currently, which my next patch will add to
> kernfs_create_dir_ns(). It cannot (easily) be added to
> cgroup_kn_set_ugid() because we can't dereference struct kernfs_iattrs
> from there.
>
> Signed-off-by: Max Kellermann <max.kellermann@xxxxxxxxx>
> Acked-by: Tejun Heo <tj@xxxxxxxxxx>
> --
> v1 -> v2: 12-digit commit id
> ---
> kernel/cgroup/cgroup.c | 31 ++++---------------------------
> 1 file changed, 4 insertions(+), 27 deletions(-)
>
> diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
> index 4b9ff41ca603..a844b421fd83 100644
> --- a/kernel/cgroup/cgroup.c
> +++ b/kernel/cgroup/cgroup.c
> @@ -4169,20 +4169,6 @@ static struct kernfs_ops cgroup_kf_ops = {
> .seq_show = cgroup_seqfile_show,
> };
>
> -/* set uid and gid of cgroup dirs and files to that of the creator */
> -static int cgroup_kn_set_ugid(struct kernfs_node *kn)
> -{
> - struct iattr iattr = { .ia_valid = ATTR_UID | ATTR_GID,
> - .ia_uid = current_fsuid(),
> - .ia_gid = current_fsgid(), };
> -
> - if (uid_eq(iattr.ia_uid, GLOBAL_ROOT_UID) &&
> - gid_eq(iattr.ia_gid, GLOBAL_ROOT_GID))
> - return 0;
> -
> - return kernfs_setattr(kn, &iattr);
> -}
> -
> static void cgroup_file_notify_timer(struct timer_list *timer)
> {
> cgroup_file_notify(container_of(timer, struct cgroup_file,
> @@ -4195,25 +4181,18 @@ static int cgroup_add_file(struct cgroup_subsys_state *css, struct cgroup *cgrp,
> char name[CGROUP_FILE_NAME_MAX];
> struct kernfs_node *kn;
> struct lock_class_key *key = NULL;
> - int ret;
>
> #ifdef CONFIG_DEBUG_LOCK_ALLOC
> key = &cft->lockdep_key;
> #endif
> kn = __kernfs_create_file(cgrp->kn, cgroup_file_name(cgrp, cft, name),
> cgroup_file_mode(cft),
> - GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
> + current_fsuid(), current_fsgid(),
> 0, cft->kf_ops, cft,
> NULL, key);
> if (IS_ERR(kn))
> return PTR_ERR(kn);
>
> - ret = cgroup_kn_set_ugid(kn);
> - if (ret) {
> - kernfs_remove(kn);
> - return ret;
> - }
> -
> if (cft->file_offset) {
> struct cgroup_file *cfile = (void *)css + cft->file_offset;
>
> @@ -5616,7 +5595,9 @@ static struct cgroup *cgroup_create(struct cgroup *parent, const char *name,
> goto out_cancel_ref;
>
> /* create the directory */
> - kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
> + kn = kernfs_create_dir_ns(parent->kn, name, mode,
> + current_fsuid(), current_fsgid(),
> + cgrp, NULL);
> if (IS_ERR(kn)) {
> ret = PTR_ERR(kn);
> goto out_stat_exit;
> @@ -5761,10 +5742,6 @@ int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, umode_t mode)
> */
> kernfs_get(cgrp->kn);
>
> - ret = cgroup_kn_set_ugid(cgrp->kn);
> - if (ret)
> - goto out_destroy;
> -
> ret = css_populate_dir(&cgrp->self);
> if (ret)
> goto out_destroy;
No noticeable regressions with this patch applied.
Tested-by: Bagas Sanjaya <bagasdotme@xxxxxxxxx>
--
An old man doll... just what I always wanted! - Clara
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