From 4534dee941056a4ab9dca4a9e2edff28692800b2 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Michal=20Koutn=C3=BD?= Date: Fri, 26 Aug 2022 18:52:36 +0200 Subject: [PATCH] cgroup: cgroup: Honor caller's cgroup NS when resolving cgroup id MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Cgroup ids are resolved in the global scope. That may be needed sometime (in future) but currently it violates virtual view provided through cgroup namespaces. There are currently following users of the resolution: - fc_appid_store - bpf_iter_attach_cgroup - mem_cgroup_get_from_ino None of the is a called on behalf of kernel but the resolution is made with proper userspace context, hence the default to current->nsproxy makes sens. (This doesn't rule out cgroup_get_from_id with cgroup NS parameter in the future.) Since cgroup ids are defined on v2 hierarchy only, we simply check existence in the cgroup namespace by looking at ancestry on the default hierarchy. Fixes: 6b658c4863c1 ("scsi: cgroup: Add cgroup_get_from_id()") Signed-off-by: Michal Koutný Signed-off-by: Tejun Heo --- kernel/cgroup/cgroup.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 1c7ab41..3229f35 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -6006,11 +6006,12 @@ void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen) * cgroup_get_from_id : get the cgroup associated with cgroup id * @id: cgroup id * On success return the cgrp, on failure return NULL + * Only cgroups within current task's cgroup NS are valid. */ struct cgroup *cgroup_get_from_id(u64 id) { struct kernfs_node *kn; - struct cgroup *cgrp = NULL; + struct cgroup *cgrp = NULL, *root_cgrp; kn = kernfs_find_and_get_node_by_id(cgrp_dfl_root.kf_root, id); if (!kn) @@ -6023,8 +6024,18 @@ struct cgroup *cgroup_get_from_id(u64 id) cgrp = NULL; rcu_read_unlock(); - kernfs_put(kn); + + if (!cgrp) + goto out; + + spin_lock_irq(&css_set_lock); + root_cgrp = current_cgns_cgroup_from_root(&cgrp_dfl_root); + spin_unlock_irq(&css_set_lock); + if (!cgroup_is_descendant(cgrp, root_cgrp)) { + cgroup_put(cgrp); + cgrp = NULL; + } out: return cgrp; } -- 2.7.4