From ab1de7ead871ebe6d12a774c3c25de0388cde082 Mon Sep 17 00:00:00 2001
From: Qi Zheng
Date: Wed, 17 May 2023 07:45:45 +0000
Subject: cgroup: fix missing cpus_read_{lock,unlock}() in
cgroup_transfer_tasks()
The commit 4f7e7236435c ("cgroup: Fix threadgroup_rwsem <-> cpus_read_lock()
deadlock") fixed the deadlock between cgroup_threadgroup_rwsem and
cpus_read_lock() by introducing cgroup_attach_{lock,unlock}() and removing
cpus_read_{lock,unlock}() from cpuset_attach(). But cgroup_transfer_tasks()
was missed and not handled, which will cause th following warning:
WARNING: CPU: 0 PID: 589 at kernel/cpu.c:526 lockdep_assert_cpus_held+0x32/0x40
CPU: 0 PID: 589 Comm: kworker/1:4 Not tainted 6.4.0-rc2-next-20230517 #50
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
Workqueue: events cpuset_hotplug_workfn
RIP: 0010:lockdep_assert_cpus_held+0x32/0x40
<...>
Call Trace:
cpuset_attach+0x40/0x240
cgroup_migrate_execute+0x452/0x5e0
? _raw_spin_unlock_irq+0x28/0x40
cgroup_transfer_tasks+0x1f3/0x360
? find_held_lock+0x32/0x90
? cpuset_hotplug_workfn+0xc81/0xed0
cpuset_hotplug_workfn+0xcb1/0xed0
? process_one_work+0x248/0x5b0
process_one_work+0x2b9/0x5b0
worker_thread+0x56/0x3b0
? process_one_work+0x5b0/0x5b0
kthread+0xf1/0x120
? kthread_complete_and_exit+0x20/0x20
ret_from_fork+0x1f/0x30
So just use the cgroup_attach_{lock,unlock}() helper to fix it.
Reported-by: Zhao Gongyi
Signed-off-by: Qi Zheng
Acked-by: Muchun Song
Fixes: 05c7b7a92cc8 ("cgroup/cpuset: Fix a race between cpuset_attach() and cpu hotplug")
Cc: stable@vger.kernel.org # v5.17+
Signed-off-by: Tejun Heo
---
kernel/cgroup/cgroup-v1.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
(limited to 'kernel')
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index aeef06c465ef..5407241dbb45 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -108,7 +108,7 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
cgroup_lock();
- percpu_down_write(&cgroup_threadgroup_rwsem);
+ cgroup_attach_lock(true);
/* all tasks in @from are being moved, all csets are source */
spin_lock_irq(&css_set_lock);
@@ -144,7 +144,7 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
} while (task && !ret);
out_err:
cgroup_migrate_finish(&mgctx);
- percpu_up_write(&cgroup_threadgroup_rwsem);
+ cgroup_attach_unlock(true);
cgroup_unlock();
return ret;
}
--
cgit v1.2.3
From 2bd110339288c18823dcace602b63b0d8627e520 Mon Sep 17 00:00:00 2001
From: John Sperbeck
Date: Sun, 21 May 2023 19:29:53 +0000
Subject: cgroup: always put cset in cgroup_css_set_put_fork
A successful call to cgroup_css_set_fork() will always have taken
a ref on kargs->cset (regardless of CLONE_INTO_CGROUP), so always
do a corresponding put in cgroup_css_set_put_fork().
Without this, a cset and its contained css structures will be
leaked for some fork failures. The following script reproduces
the leak for a fork failure due to exceeding pids.max in the
pids controller. A similar thing can happen if we jump to the
bad_fork_cancel_cgroup label in copy_process().
[ -z "$1" ] && echo "Usage $0 pids-root" && exit 1
PID_ROOT=$1
CGROUP=$PID_ROOT/foo
[ -e $CGROUP ] && rmdir -f $CGROUP
mkdir $CGROUP
echo 5 > $CGROUP/pids.max
echo $$ > $CGROUP/cgroup.procs
fork_bomb()
{
set -e
for i in $(seq 10); do
/bin/sleep 3600 &
done
}
(fork_bomb) &
wait
echo $$ > $PID_ROOT/cgroup.procs
kill $(cat $CGROUP/cgroup.procs)
rmdir $CGROUP
Fixes: ef2c41cf38a7 ("clone3: allow spawning processes into cgroups")
Cc: stable@vger.kernel.org # v5.7+
Signed-off-by: John Sperbeck
Signed-off-by: Tejun Heo
---
kernel/cgroup/cgroup.c | 17 ++++++++---------
1 file changed, 8 insertions(+), 9 deletions(-)
(limited to 'kernel')
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 625d7483951c..245cf62ce85a 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -6486,19 +6486,18 @@ err:
static void cgroup_css_set_put_fork(struct kernel_clone_args *kargs)
__releases(&cgroup_threadgroup_rwsem) __releases(&cgroup_mutex)
{
+ struct cgroup *cgrp = kargs->cgrp;
+ struct css_set *cset = kargs->cset;
+
cgroup_threadgroup_change_end(current);
- if (kargs->flags & CLONE_INTO_CGROUP) {
- struct cgroup *cgrp = kargs->cgrp;
- struct css_set *cset = kargs->cset;
+ if (cset) {
+ put_css_set(cset);
+ kargs->cset = NULL;
+ }
+ if (kargs->flags & CLONE_INTO_CGROUP) {
cgroup_unlock();
-
- if (cset) {
- put_css_set(cset);
- kargs->cset = NULL;
- }
-
if (cgrp) {
cgroup_put(cgrp);
kargs->cgrp = NULL;
--
cgit v1.2.3