linux-kernel - [PATCH rcu 6/8] rcu: Mark rcu_cpu_kthread() accesses to ->rcu_cpu_has

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20230510165832.2187453-6-paulmck@kernel.org>
Date:   Wed, 10 May 2023 09:58:30 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...a.com,
        rostedt@...dmis.org, "Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH rcu 6/8] rcu: Mark rcu_cpu_kthread() accesses to ->rcu_cpu_has_work

The rcu_data structure's ->rcu_cpu_has_work field can be modified by
any CPU attempting to wake up the rcuc kthread.  Therefore, this commit
marks accesses to this field from the rcu_cpu_kthread() function.

This data race was reported by KCSAN.  Not appropriate for backporting
due to failure being unlikely.

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/tree.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index e2dbea6cee4b..faa1c01d2917 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2481,12 +2481,12 @@ static void rcu_cpu_kthread(unsigned int cpu)
 		*statusp = RCU_KTHREAD_RUNNING;
 		local_irq_disable();
 		work = *workp;
-		*workp = 0;
+		WRITE_ONCE(*workp, 0);
 		local_irq_enable();
 		if (work)
 			rcu_core();
 		local_bh_enable();
-		if (*workp == 0) {
+		if (!READ_ONCE(*workp)) {
 			trace_rcu_utilization(TPS("End CPU kthread@..._wait"));
 			*statusp = RCU_KTHREAD_WAITING;
 			return;
-- 
2.40.1