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cgroup/cpuset: Make child cpusets restrict parents on v1 hierarchy

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The commit 1f1562fcd04a ("cgroup/cpuset: Don't let child cpusets
restrict parent in default hierarchy") inteded to relax the check only
on the default hierarchy (or v2 mode) but it dropped the check in v1
too.

This patch returns and separates the legacy-only validations so that
they can be considered only in the v1 mode, which should enforce the old
constraints for the sake of compatibility.

Fixes: 1f1562fcd04a ("cgroup/cpuset: Don't let child cpusets restrict parent in default hierarchy")
Suggested-by: Waiman Long <longman@redhat.com>
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Michal Koutný 2021-12-17 16:48:54 +01:00 committed by Tejun Heo
parent daadb3bd0e
commit d068eebbd4
1 changed files with 40 additions and 12 deletions
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52
kernel/cgroup/cpuset.c
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@ -590,6 +590,35 @@ static inline void free_cpuset(struct cpuset *cs)
kfree(cs); kfree(cs);
} }
/*
* validate_change_legacy() - Validate conditions specific to legacy (v1)
* behavior.
*/
static int validate_change_legacy(struct cpuset *cur, struct cpuset *trial)
{
struct cgroup_subsys_state *css;
struct cpuset *c, *par;
int ret;
WARN_ON_ONCE(!rcu_read_lock_held());
/* Each of our child cpusets must be a subset of us */
ret = -EBUSY;
cpuset_for_each_child(c, css, cur)
if (!is_cpuset_subset(c, trial))
goto out;
/* On legacy hierarchy, we must be a subset of our parent cpuset. */
ret = -EACCES;
par = parent_cs(cur);
if (par && !is_cpuset_subset(trial, par))
goto out;
ret = 0;
out:
return ret;
}
/* /*
* validate_change() - Used to validate that any proposed cpuset change * validate_change() - Used to validate that any proposed cpuset change
* follows the structural rules for cpusets. * follows the structural rules for cpusets.
@ -614,20 +643,21 @@ static int validate_change(struct cpuset *cur, struct cpuset *trial)
{ {
struct cgroup_subsys_state *css; struct cgroup_subsys_state *css;
struct cpuset *c, *par; struct cpuset *c, *par;
int ret; int ret = 0;
/* The checks don't apply to root cpuset */
if (cur == &top_cpuset)
return 0;
rcu_read_lock(); rcu_read_lock();
par = parent_cs(cur);
/* On legacy hierarchy, we must be a subset of our parent cpuset. */ if (!is_in_v2_mode())
ret = -EACCES; ret = validate_change_legacy(cur, trial);
if (!is_in_v2_mode() && !is_cpuset_subset(trial, par)) if (ret)
goto out; goto out;
/* Remaining checks don't apply to root cpuset */
if (cur == &top_cpuset)
goto out;
par = parent_cs(cur);
/* /*
* If either I or some sibling (!= me) is exclusive, we can't * If either I or some sibling (!= me) is exclusive, we can't
* overlap * overlap
@ -1175,9 +1205,7 @@ enum subparts_cmd {
* *
* Because of the implicit cpu exclusive nature of a partition root, * Because of the implicit cpu exclusive nature of a partition root,
* cpumask changes that violates the cpu exclusivity rule will not be * cpumask changes that violates the cpu exclusivity rule will not be
* permitted when checked by validate_change(). The validate_change() * permitted when checked by validate_change().
* function will also prevent any changes to the cpu list if it is not
* a superset of children's cpu lists.
*/ */
static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd, static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
struct cpumask *newmask, struct cpumask *newmask,