linux-kernel - [PATCH 1/4] cgroup: Honor caller's cgroup NS when resolving path

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Message-Id: <20220826165238.30915-2-mkoutny@suse.com>
Date:   Fri, 26 Aug 2022 18:52:35 +0200
From:   Michal Koutný <mkoutny@...e.com>
To:     linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        bpf@...r.kernel.org
Cc:     Tejun Heo <tj@...nel.org>, Aditya Kali <adityakali@...gle.com>,
        Serge Hallyn <serge.hallyn@...onical.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Yonghong Song <yhs@...com>,
        Muneendra Kumar <muneendra.kumar@...adcom.com>,
        Yosry Ahmed <yosryahmed@...gle.com>,
        Hao Luo <haoluo@...gle.com>
Subject: [PATCH 1/4] cgroup: Honor caller's cgroup NS when resolving path

cgroup_get_from_path() is not widely used function. Its callers presume
the path is resolved under cgroup namespace. (There is one caller
currently and resolving in init NS won't make harm (netfilter). However,
future users may be subject to different effects when resolving
globally.)
Since, there's currently no use for the global resolution, modify the
existing function to take cgroup NS into account.

Fixes: a79a908fd2b0 ("cgroup: introduce cgroup namespaces")
Signed-off-by: Michal Koutný <mkoutny@...e.com>
---
 kernel/cgroup/cgroup.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 5f4502aa2b3b..1a8b50d15ebf 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -6598,8 +6598,12 @@ struct cgroup *cgroup_get_from_path(const char *path)
 {
 	struct kernfs_node *kn;
 	struct cgroup *cgrp = ERR_PTR(-ENOENT);
+	struct cgroup *root_cgrp;
 
-	kn = kernfs_walk_and_get(cgrp_dfl_root.cgrp.kn, path);
+	spin_lock_irq(&css_set_lock);
+	root_cgrp = current_cgns_cgroup_from_root(&cgrp_dfl_root);
+	kn = kernfs_walk_and_get(root_cgrp->kn, path);
+	spin_unlock_irq(&css_set_lock);
 	if (!kn)
 		goto out;
 
-- 
2.37.0