This is a note to let you know that I've just added the patch titled
cgroup: Fix suspicious rcu_dereference_check() usage warning
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
cgroup-fix-suspicious-rcu_dereference_check-usage-wa.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 252ce073c79006ca4713d9d789b5c7dd343a42a3
Author: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Date: Fri Sep 29 16:16:07 2023 +0300
cgroup: Fix suspicious rcu_dereference_check() usage warning
commit f2aa197e4794bf4c2c0c9570684f86e6fa103e8b upstream.
task_css_set_check() will use rcu_dereference_check() to check for
rcu_read_lock_held() on the read-side, which is not true after commit
dc6e0818bc9a ("sched/cpuacct: Optimize away RCU read lock"). This
commit drop explicit rcu_read_lock(), change to RCU-sched read-side
critical section. So fix the RCU warning by adding check for
rcu_read_lock_sched_held().
Fixes: dc6e0818bc9a ("sched/cpuacct: Optimize away RCU read lock")
Reported-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx>
Reported-by: syzbot+16e3f2c77e7c5a0113f9@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Tested-by: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx>
Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20220305034103.57123-1-zhouchengming@xxxxxxxxxxxxx
Signed-off-by: Ovidiu Panait <ovidiu.panait@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index f425389ce4bb2..0d97d1cf660f7 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -451,6 +451,7 @@ extern struct mutex cgroup_mutex;
extern spinlock_t css_set_lock;
#define task_css_set_check(task, __c) \
rcu_dereference_check((task)->cgroups, \
+ rcu_read_lock_sched_held() || \
lockdep_is_held(&cgroup_mutex) || \
lockdep_is_held(&css_set_lock) || \
((task)->flags & PF_EXITING) || (__c))
