On 4/17/23 04:04, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x eee87853794187f6adbe19533ed79c8b44b36a91
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2023041702-vertebrae-bonsai-f1de@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..
Possible dependencies:
eee878537941 ("cgroup/cpuset: Add cpuset_can_fork() and cpuset_cancel_fork() methods")
42a11bf5c543 ("cgroup/cpuset: Make cpuset_fork() handle CLONE_INTO_CGROUP properly")
18f9a4d47527 ("cgroup/cpuset: Skip spread flags update on v2")
I have posted a patch series that also include commit 18f9a4d47527
("cgroup/cpuset: Skip spread flags update on v2") which is not
technically a fix but is relative simple and low risk.
Cheers,
Longman
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From eee87853794187f6adbe19533ed79c8b44b36a91 Mon Sep 17 00:00:00 2001
From: Waiman Long <longman@xxxxxxxxxx>
Date: Tue, 11 Apr 2023 09:35:59 -0400
Subject: [PATCH] cgroup/cpuset: Add cpuset_can_fork() and cpuset_cancel_fork()
methods
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
In the case of CLONE_INTO_CGROUP, not all cpusets are ready to accept
new tasks. It is too late to check that in cpuset_fork(). So we need
to add the cpuset_can_fork() and cpuset_cancel_fork() methods to
pre-check it before we can allow attachment to a different cpuset.
We also need to set the attach_in_progress flag to alert other code
that a new task is going to be added to the cpuset.
Fixes: ef2c41cf38a7 ("clone3: allow spawning processes into cgroups")
Suggested-by: Michal Koutný <mkoutny@xxxxxxxx>
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v5.7+
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 2ccfae74acf9..166a45019f66 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -2453,6 +2453,20 @@ static int fmeter_getrate(struct fmeter *fmp)
static struct cpuset *cpuset_attach_old_cs;
+/*
+ * Check to see if a cpuset can accept a new task
+ * For v1, cpus_allowed and mems_allowed can't be empty.
+ * For v2, effective_cpus can't be empty.
+ * Note that in v1, effective_cpus = cpus_allowed.
+ */
+static int cpuset_can_attach_check(struct cpuset *cs)
+{
+ if (cpumask_empty(cs->effective_cpus) ||
+ (!is_in_v2_mode() && nodes_empty(cs->mems_allowed)))
+ return -ENOSPC;
+ return 0;
+}
+
/* Called by cgroups to determine if a cpuset is usable; cpuset_rwsem held */
static int cpuset_can_attach(struct cgroup_taskset *tset)
{
@@ -2467,16 +2481,9 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
percpu_down_write(&cpuset_rwsem);
- /* allow moving tasks into an empty cpuset if on default hierarchy */
- ret = -ENOSPC;
- if (!is_in_v2_mode() &&
- (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed)))
- goto out_unlock;
-
- /*
- * Task cannot be moved to a cpuset with empty effective cpus.
- */
- if (cpumask_empty(cs->effective_cpus))
+ /* Check to see if task is allowed in the cpuset */
+ ret = cpuset_can_attach_check(cs);
+ if (ret)
goto out_unlock;
cgroup_taskset_for_each(task, css, tset) {
@@ -2493,7 +2500,6 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
* changes which zero cpus/mems_allowed.
*/
cs->attach_in_progress++;
- ret = 0;
out_unlock:
percpu_up_write(&cpuset_rwsem);
return ret;
@@ -3264,6 +3270,68 @@ static void cpuset_bind(struct cgroup_subsys_state *root_css)
percpu_up_write(&cpuset_rwsem);
}
+/*
+ * In case the child is cloned into a cpuset different from its parent,
+ * additional checks are done to see if the move is allowed.
+ */
+static int cpuset_can_fork(struct task_struct *task, struct css_set *cset)
+{
+ struct cpuset *cs = css_cs(cset->subsys[cpuset_cgrp_id]);
+ bool same_cs;
+ int ret;
+
+ rcu_read_lock();
+ same_cs = (cs == task_cs(current));
+ rcu_read_unlock();
+
+ if (same_cs)
+ return 0;
+
+ lockdep_assert_held(&cgroup_mutex);
+ percpu_down_write(&cpuset_rwsem);
+
+ /* Check to see if task is allowed in the cpuset */
+ ret = cpuset_can_attach_check(cs);
+ if (ret)
+ goto out_unlock;
+
+ ret = task_can_attach(task, cs->effective_cpus);
+ if (ret)
+ goto out_unlock;
+
+ ret = security_task_setscheduler(task);
+ if (ret)
+ goto out_unlock;
+
+ /*
+ * Mark attach is in progress. This makes validate_change() fail
+ * changes which zero cpus/mems_allowed.
+ */
+ cs->attach_in_progress++;
+out_unlock:
+ percpu_up_write(&cpuset_rwsem);
+ return ret;
+}
+
+static void cpuset_cancel_fork(struct task_struct *task, struct css_set *cset)
+{
+ struct cpuset *cs = css_cs(cset->subsys[cpuset_cgrp_id]);
+ bool same_cs;
+
+ rcu_read_lock();
+ same_cs = (cs == task_cs(current));
+ rcu_read_unlock();
+
+ if (same_cs)
+ return;
+
+ percpu_down_write(&cpuset_rwsem);
+ cs->attach_in_progress--;
+ if (!cs->attach_in_progress)
+ wake_up(&cpuset_attach_wq);
+ percpu_up_write(&cpuset_rwsem);
+}
+
/*
* Make sure the new task conform to the current state of its parent,
* which could have been changed by cpuset just after it inherits the
@@ -3292,6 +3360,11 @@ static void cpuset_fork(struct task_struct *task)
percpu_down_write(&cpuset_rwsem);
guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
cpuset_attach_task(cs, task);
+
+ cs->attach_in_progress--;
+ if (!cs->attach_in_progress)
+ wake_up(&cpuset_attach_wq);
+
percpu_up_write(&cpuset_rwsem);
}
@@ -3305,6 +3378,8 @@ struct cgroup_subsys cpuset_cgrp_subsys = {
.attach = cpuset_attach,
.post_attach = cpuset_post_attach,
.bind = cpuset_bind,
+ .can_fork = cpuset_can_fork,
+ .cancel_fork = cpuset_cancel_fork,
.fork = cpuset_fork,
.legacy_cftypes = legacy_files,
.dfl_cftypes = dfl_files,
