linux-kernel - [PATCH v2 2/4] wireguard: fix wg_cpumask_choose

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Message-Id: <20230306210312.2614988-3-vernon2gm@gmail.com>
Date:   Tue,  7 Mar 2023 05:03:10 +0800
From:   Vernon Yang <vernon2gm@...il.com>
To:     torvalds@...ux-foundation.org, tytso@....edu, Jason@...c4.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, jejb@...ux.ibm.com, martin.petersen@...cle.com,
        yury.norov@...il.com, andriy.shevchenko@...ux.intel.com,
        linux@...musvillemoes.dk, james.smart@...adcom.com,
        dick.kennedy@...adcom.com
Cc:     linux-kernel@...r.kernel.org, wireguard@...ts.zx2c4.com,
        netdev@...r.kernel.org, linux-scsi@...r.kernel.org,
        Vernon Yang <vernon2gm@...il.com>
Subject: [PATCH v2 2/4] wireguard: fix wg_cpumask_choose_online() if no further cpus set

When cpumask_next() the return value is greater than or equal to
nr_cpu_ids, it indicates invalid.

Before commit 596ff4a09b89 ("cpumask: re-introduce constant-sized cpumask
optimizations"), when cpumask_next() returned an invalid cpu, the driver
used the judgment equal to nr_cpu_ids to indicate the invalid cpu, so it
happened to work normally, but this is the wrong approach.

After commit 596ff4a09b89 ("cpumask: re-introduce constant-sized cpumask
optimizations"), these incorrect practices actively buggy, so fix it to
correctly.

Signed-off-by: Vernon Yang <vernon2gm@...il.com>
---
 drivers/net/wireguard/queueing.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireguard/queueing.h b/drivers/net/wireguard/queueing.h
index 583adb37ee1e..125284b346a7 100644
--- a/drivers/net/wireguard/queueing.h
+++ b/drivers/net/wireguard/queueing.h
@@ -106,7 +106,7 @@ static inline int wg_cpumask_choose_online(int *stored_cpu, unsigned int id)
 {
 	unsigned int cpu = *stored_cpu, cpu_index, i;
 
-	if (unlikely(cpu == nr_cpumask_bits ||
+	if (unlikely(cpu >= nr_cpu_ids ||
 		     !cpumask_test_cpu(cpu, cpu_online_mask))) {
 		cpu_index = id % cpumask_weight(cpu_online_mask);
 		cpu = cpumask_first(cpu_online_mask);
-- 
2.34.1