The patch below does not apply to the 5.10-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@vger.kernel.org.

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-5.10.y git checkout FETCH_HEAD git cherry-pick -x 42a11bf5c5436e91b040aeb04063be1710bb9f9c # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2023041751-latter-oaf-71e3@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

42a11bf5c543 ("cgroup/cpuset: Make cpuset_fork() handle CLONE_INTO_CGROUP properly") 18f9a4d47527 ("cgroup/cpuset: Skip spread flags update on v2") b94f9ac79a73 ("cgroup/cpuset: Change references of cpuset_mutex to cpuset_rwsem") 69dc8010b8fc ("Merge branch 'for-5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 42a11bf5c5436e91b040aeb04063be1710bb9f9c Mon Sep 17 00:00:00 2001 From: Waiman Long longman@redhat.com Date: Tue, 11 Apr 2023 09:35:58 -0400 Subject: [PATCH] cgroup/cpuset: Make cpuset_fork() handle CLONE_INTO_CGROUP properly

By default, the clone(2) syscall spawn a child process into the same cgroup as its parent. With the use of the CLONE_INTO_CGROUP flag introduced by commit ef2c41cf38a7 ("clone3: allow spawning processes into cgroups"), the child will be spawned into a different cgroup which is somewhat similar to writing the child's tid into "cgroup.threads".

The current cpuset_fork() method does not properly handle the CLONE_INTO_CGROUP case where the cpuset of the child may be different from that of its parent. Update the cpuset_fork() method to treat the CLONE_INTO_CGROUP case similar to cpuset_attach().

Since the newly cloned task has not been running yet, its actual memory usage isn't known. So it is not necessary to make change to mm in cpuset_fork().

Fixes: ef2c41cf38a7 ("clone3: allow spawning processes into cgroups") Reported-by: Giuseppe Scrivano gscrivan@redhat.com Signed-off-by: Waiman Long longman@redhat.com Cc: stable@vger.kernel.org # v5.7+ Signed-off-by: Tejun Heo tj@kernel.org

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index ff7eb8e2efdc..2ccfae74acf9 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -2515,16 +2515,33 @@ static void cpuset_cancel_attach(struct cgroup_taskset *tset) }

/* - * Protected by cpuset_rwsem. cpus_attach is used only by cpuset_attach() + * Protected by cpuset_rwsem. cpus_attach is used only by cpuset_attach_task() * but we can't allocate it dynamically there. Define it global and * allocate from cpuset_init(). */ static cpumask_var_t cpus_attach; +static nodemask_t cpuset_attach_nodemask_to; + +static void cpuset_attach_task(struct cpuset *cs, struct task_struct *task) +{ + percpu_rwsem_assert_held(&cpuset_rwsem); + + if (cs != &top_cpuset) + guarantee_online_cpus(task, cpus_attach); + else + cpumask_copy(cpus_attach, task_cpu_possible_mask(task)); + /* + * can_attach beforehand should guarantee that this doesn't + * fail. TODO: have a better way to handle failure here + */ + WARN_ON_ONCE(set_cpus_allowed_ptr(task, cpus_attach)); + + cpuset_change_task_nodemask(task, &cpuset_attach_nodemask_to); + cpuset_update_task_spread_flags(cs, task); +}

static void cpuset_attach(struct cgroup_taskset *tset) { - /* static buf protected by cpuset_rwsem */ - static nodemask_t cpuset_attach_nodemask_to; struct task_struct *task; struct task_struct *leader; struct cgroup_subsys_state *css; @@ -2555,20 +2572,8 @@ static void cpuset_attach(struct cgroup_taskset *tset)

guarantee_online_mems(cs, &cpuset_attach_nodemask_to);

- cgroup_taskset_for_each(task, css, tset) { - if (cs != &top_cpuset) - guarantee_online_cpus(task, cpus_attach); - else - cpumask_copy(cpus_attach, task_cpu_possible_mask(task)); - /* - * can_attach beforehand should guarantee that this doesn't - * fail. TODO: have a better way to handle failure here - */ - WARN_ON_ONCE(set_cpus_allowed_ptr(task, cpus_attach)); - - cpuset_change_task_nodemask(task, &cpuset_attach_nodemask_to); - cpuset_update_task_spread_flags(cs, task); - } + cgroup_taskset_for_each(task, css, tset) + cpuset_attach_task(cs, task);

/* * Change mm for all threadgroup leaders. This is expensive and may @@ -3266,11 +3271,28 @@ static void cpuset_bind(struct cgroup_subsys_state *root_css) */ static void cpuset_fork(struct task_struct *task) { - if (task_css_is_root(task, cpuset_cgrp_id)) + struct cpuset *cs; + bool same_cs; + + rcu_read_lock(); + cs = task_cs(task); + same_cs = (cs == task_cs(current)); + rcu_read_unlock(); + + if (same_cs) { + if (cs == &top_cpuset) + return; + + set_cpus_allowed_ptr(task, current->cpus_ptr); + task->mems_allowed = current->mems_allowed; return; + }

- set_cpus_allowed_ptr(task, current->cpus_ptr); - task->mems_allowed = current->mems_allowed; + /* CLONE_INTO_CGROUP */ + percpu_down_write(&cpuset_rwsem); + guarantee_online_mems(cs, &cpuset_attach_nodemask_to); + cpuset_attach_task(cs, task); + percpu_up_write(&cpuset_rwsem); }

struct cgroup_subsys cpuset_cgrp_subsys = {