[PATCH 5.13 171/300] cgroup/cpuset: Fix violation of cpuset locking rule

Greg Kroah-Hartman
2021-09-13T14:07:35Z

From: Waiman Long <longman@redhat.com>

[ Upstream commit 6ba34d3c73674e46d9e126e4f0cee79e5ef2481c ]

The cpuset fields that manage partition root state do not strictly
follow the cpuset locking rule that update to cpuset has to be done
with both the callback_lock and cpuset_mutex held. This is now fixed
by making sure that the locking rule is upheld.

Fixes: 3881b86128d0 ("cpuset: Add an error state to cpuset.sched.partition")
Fixes: 4b842da276a8 ("cpuset: Make CPU hotplug work with partition")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/cgroup/cpuset.c | 58 +++++++++++++++++++++++++-----------------
1 file changed, 35 insertions(+), 23 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 28a784bf64b1..13b5be6df4da 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1148,6 +1148,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
struct cpuset *parent = parent_cs(cpuset);
int adding; /* Moving cpus from effective_cpus to subparts_cpus */
int deleting; /* Moving cpus from subparts_cpus to effective_cpus */
+ int new_prs;
bool part_error = false; /* Partition error? */

percpu_rwsem_assert_held(&cpuset_rwsem);
@@ -1183,6 +1184,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
* A cpumask update cannot make parent's effective_cpus become empty.
*/
adding = deleting = false;
+ new_prs = cpuset->partition_root_state;
if (cmd == partcmd_enable) {
cpumask_copy(tmp->addmask, cpuset->cpus_allowed);
adding = true;
@@ -1247,11 +1249,11 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
switch (cpuset->partition_root_state) {
case PRS_ENABLED:
if (part_error)
- cpuset->partition_root_state = PRS_ERROR;
+ new_prs = PRS_ERROR;
break;
case PRS_ERROR:
if (!part_error)
- cpuset->partition_root_state = PRS_ENABLED;
+ new_prs = PRS_ENABLED;
break;
}
/*
@@ -1260,10 +1262,10 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
part_error = (prev_prs == PRS_ERROR);
}

- if (!part_error && (cpuset->partition_root_state == PRS_ERROR))
+ if (!part_error && (new_prs == PRS_ERROR))
return 0; /* Nothing need to be done */

- if (cpuset->partition_root_state == PRS_ERROR) {
+ if (new_prs == PRS_ERROR) {
/*
* Remove all its cpus from parent's subparts_cpus.
*/
@@ -1272,7 +1274,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
parent->subparts_cpus);
}

- if (!adding && !deleting)
+ if (!adding && !deleting && (new_prs == cpuset->partition_root_state))
return 0;

/*
@@ -1299,6 +1301,9 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
}

parent->nr_subparts_cpus = cpumask_weight(parent->subparts_cpus);
+
+ if (cpuset->partition_root_state != new_prs)
+ cpuset->partition_root_state = new_prs;
spin_unlock_irq(&callback_lock);

return cmd == partcmd_update;
@@ -1321,6 +1326,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
struct cpuset *cp;
struct cgroup_subsys_state *pos_css;
bool need_rebuild_sched_domains = false;
+ int new_prs;

rcu_read_lock();
cpuset_for_each_descendant_pre(cp, pos_css, cs) {
@@ -1360,7 +1366,8 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
* update_tasks_cpumask() again for tasks in the parent
* cpuset if the parent's subparts_cpus changes.
*/
- if ((cp != cs) && cp->partition_root_state) {
+ new_prs = cp->partition_root_state;
+ if ((cp != cs) && new_prs) {
switch (parent->partition_root_state) {
case PRS_DISABLED:
/*
@@ -1370,7 +1377,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
*/
WARN_ON_ONCE(cp->partition_root_state
!= PRS_ERROR);
- cp->partition_root_state = PRS_DISABLED;
+ new_prs = PRS_DISABLED;

/*
* clear_bit() is an atomic operation and
@@ -1391,11 +1398,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
/*
* When parent is invalid, it has to be too.
*/
- cp->partition_root_state = PRS_ERROR;
- if (cp->nr_subparts_cpus) {
- cp->nr_subparts_cpus = 0;
- cpumask_clear(cp->subparts_cpus);
- }
+ new_prs = PRS_ERROR;
break;
}
}
@@ -1407,8 +1410,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
spin_lock_irq(&callback_lock);

cpumask_copy(cp->effective_cpus, tmp->new_cpus);
- if (cp->nr_subparts_cpus &&
- (cp->partition_root_state != PRS_ENABLED)) {
+ if (cp->nr_subparts_cpus && (new_prs != PRS_ENABLED)) {
cp->nr_subparts_cpus = 0;
cpumask_clear(cp->subparts_cpus);
} else if (cp->nr_subparts_cpus) {
@@ -1435,6 +1437,10 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
= cpumask_weight(cp->subparts_cpus);
}
}
+
+ if (new_prs != cp->partition_root_state)
+ cp->partition_root_state = new_prs;
+
spin_unlock_irq(&callback_lock);

WARN_ON(!is_in_v2_mode() &&
@@ -1944,25 +1950,25 @@ out:
*/
static int update_prstate(struct cpuset *cs, int new_prs)
{
- int err;
+ int err, old_prs = cs->partition_root_state;
struct cpuset *parent = parent_cs(cs);
struct tmpmasks tmpmask;

- if (new_prs == cs->partition_root_state)
+ if (old_prs == new_prs)
return 0;

/*
* Cannot force a partial or invalid partition root to a full
* partition root.
*/
- if (new_prs && (cs->partition_root_state < 0))
+ if (new_prs && (old_prs == PRS_ERROR))
return -EINVAL;

if (alloc_cpumasks(NULL, &tmpmask))
return -ENOMEM;

err = -EINVAL;
- if (!cs->partition_root_state) {
+ if (!old_prs) {
/*
* Turning on partition root requires setting the
* CS_CPU_EXCLUSIVE bit implicitly as well and cpus_allowed
@@ -1981,14 +1987,12 @@ static int update_prstate(struct cpuset *cs, int new_prs)
update_flag(CS_CPU_EXCLUSIVE, cs, 0);
goto out;
}
- cs->partition_root_state = PRS_ENABLED;
} else {
/*
* Turning off partition root will clear the
* CS_CPU_EXCLUSIVE bit.
*/
- if (cs->partition_root_state == PRS_ERROR) {
- cs->partition_root_state = PRS_DISABLED;
+ if (old_prs == PRS_ERROR) {
update_flag(CS_CPU_EXCLUSIVE, cs, 0);
err = 0;
goto out;
@@ -1999,8 +2003,6 @@ static int update_prstate(struct cpuset *cs, int new_prs)
if (err)
goto out;

- cs->partition_root_state = PRS_DISABLED;
-
/* Turning off CS_CPU_EXCLUSIVE will not return error */
update_flag(CS_CPU_EXCLUSIVE, cs, 0);
}
@@ -2017,6 +2019,12 @@ static int update_prstate(struct cpuset *cs, int new_prs)

rebuild_sched_domains_locked();
out:
+ if (!err) {
+ spin_lock_irq(&callback_lock);
+ cs->partition_root_state = new_prs;
+ spin_unlock_irq(&callback_lock);
+ }
+
free_cpumasks(NULL, &tmpmask);
return err;
}
@@ -3080,8 +3088,10 @@ retry:
if (is_partition_root(cs) && (cpumask_empty(&new_cpus) ||
(parent->partition_root_state == PRS_ERROR))) {
if (cs->nr_subparts_cpus) {
+ spin_lock_irq(&callback_lock);
cs->nr_subparts_cpus = 0;
cpumask_clear(cs->subparts_cpus);
+ spin_unlock_irq(&callback_lock);
compute_effective_cpumask(&new_cpus, cs, parent);
}

@@ -3095,7 +3105,9 @@ retry:
cpumask_empty(&new_cpus)) {
update_parent_subparts_cpumask(cs, partcmd_disable,
NULL, tmp);
+ spin_lock_irq(&callback_lock);
cs->partition_root_state = PRS_ERROR;
+ spin_unlock_irq(&callback_lock);
}
cpuset_force_rebuild();
}
--
2.30.2