linux-kernel - [PATCH rcu 7/7] scftorture: Avoid NULL pointer exception on early exit

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Date:   Wed, 21 Jul 2021 14:04:41 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com, mingo@...nel.org,
        jiangshanlai@...il.com, akpm@...ux-foundation.org,
        mathieu.desnoyers@...icios.com, josh@...htriplett.org,
        tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org,
        dhowells@...hat.com, edumazet@...gle.com, fweisbec@...il.com,
        oleg@...hat.com, joel@...lfernandes.org,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH rcu 7/7] scftorture: Avoid NULL pointer exception on early exit

When scftorture finds an error in the module parameters controlling
the relative frequencies of smp_call_function*() variants, it takes an
early exit.  So early that it has not allocated memory to track the
kthreads running the test, which results in a segfault.  This commit
therefore checks for the existence of the memory before attempting
to stop the kthreads that would otherwise have been recorded in that
non-existent memory.

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/scftorture.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/scftorture.c b/kernel/scftorture.c
index 5cf40e4383191..64a08288b1a6d 100644
--- a/kernel/scftorture.c
+++ b/kernel/scftorture.c
@@ -513,7 +513,7 @@ static void scf_torture_cleanup(void)
 		return;
 
 	WRITE_ONCE(scfdone, true);
-	if (nthreads)
+	if (nthreads && scf_stats_p)
 		for (i = 0; i < nthreads; i++)
 			torture_stop_kthread("scftorture_invoker", scf_stats_p[i].task);
 	else
-- 
2.31.1.189.g2e36527f23