linux-kernel - [PATCH] cgroup: rstat: call cgroup_rstat_updated_list with cgroup_rstat

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Message-ID: <20250401170912.2161953-1-shakeel.butt@linux.dev>
Date: Tue,  1 Apr 2025 10:09:12 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Tejun Heo <tj@...nel.org>
Cc: Johannes Weiner <hannes@...xchg.org>,
	Michal Koutný <mkoutny@...e.com>,
	Yosry Ahmed <yosry.ahmed@...ux.dev>,
	linux-mm@...ck.org,
	cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Meta kernel team <kernel-team@...a.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Breno Leitao <leitao@...ian.org>,
	Venkat Rao Bagalkote <venkat88@...ux.ibm.com>
Subject: [PATCH] cgroup: rstat: call cgroup_rstat_updated_list with cgroup_rstat_lock

The commit 093c8812de2d ("cgroup: rstat: Cleanup flushing functions and
locking") during cleanup accidentally changed the code to call
cgroup_rstat_updated_list() without cgroup_rstat_lock which is required.
Fix it.

Fixes: 093c8812de2d ("cgroup: rstat: Cleanup flushing functions and locking")
Reported-by: Jakub Kicinski <kuba@...nel.org>
Reported-by: Breno Leitao <leitao@...ian.org>
Reported-by: Venkat Rao Bagalkote <venkat88@...ux.ibm.com>
Closes: https://lore.kernel.org/all/6564c3d6-9372-4352-9847-1eb3aea07ca4@linux.ibm.com/
Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>
---
 kernel/cgroup/rstat.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
index 4bb587d5d34f..b2239156b7de 100644
--- a/kernel/cgroup/rstat.c
+++ b/kernel/cgroup/rstat.c
@@ -318,10 +318,11 @@ __bpf_kfunc void cgroup_rstat_flush(struct cgroup *cgrp)
 
 	might_sleep();
 	for_each_possible_cpu(cpu) {
-		struct cgroup *pos = cgroup_rstat_updated_list(cgrp, cpu);
+		struct cgroup *pos;
 
 		/* Reacquire for each CPU to avoid disabling IRQs too long */
 		__cgroup_rstat_lock(cgrp, cpu);
+		pos = cgroup_rstat_updated_list(cgrp, cpu);
 		for (; pos; pos = pos->rstat_flush_next) {
 			struct cgroup_subsys_state *css;
 
-- 
2.47.1