linux-kernel - [PATCH] smp: Fix a potential usage of stale nr

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Message-Id: <20200614071020.86037-1-songmuchun@bytedance.com>
Date:   Sun, 14 Jun 2020 15:10:20 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     peterz@...radead.org, tglx@...utronix.de, mingo@...nel.org,
        bigeasy@...utronix.de, namit@...are.com
Cc:     linux-kernel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>
Subject: [PATCH] smp: Fix a potential usage of stale nr_cpus

The get_option() maybe return 0, it means that the nr_cpus is
not initialized. Then we will use the stale nr_cpus to initialize
the nr_cpu_ids. So fix it.

Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
 kernel/smp.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index 472c2b274c65..2a9a04acf123 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -634,8 +634,7 @@ static int __init nrcpus(char *str)
 {
 	int nr_cpus;
 
-	get_option(&str, &nr_cpus);
-	if (nr_cpus > 0 && nr_cpus < nr_cpu_ids)
+	if (get_option(&str, &nr_cpus) && nr_cpus > 0 && nr_cpus < nr_cpu_ids)
 		nr_cpu_ids = nr_cpus;
 
 	return 0;
-- 
2.11.0