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From:   Kuniyuki Iwashima <kuniyu@amazon.com>
To:     "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>
CC:     Kuniyuki Iwashima <kuniyu@amazon.com>,
        Kuniyuki Iwashima <kuni1840@gmail.com>,
        <netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        Matthias Tafelmeier <matthias.tafelmeier@gmx.net>
Subject: [PATCH v1 net 02/15] net: Fix data-races around weight_p and dev_weight_[rt]x_bias.
Date:   Mon, 15 Aug 2022 22:23:34 -0700
Message-ID: <20220816052347.70042-3-kuniyu@amazon.com>
In-Reply-To: <20220816052347.70042-1-kuniyu@amazon.com>
References: <20220816052347.70042-1-kuniyu@amazon.com>
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While reading weight_p and dev_weight_[rt]x_bias, they can be changed
concurrently.  Thus, we need to add READ_ONCE() to their readers.

Fixes: 3d48b53fb2ae ("net: dev_weight: TX/RX orthogonality")
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
CC: Matthias Tafelmeier <matthias.tafelmeier@gmx.net>
---
 net/core/dev.c             | 2 +-
 net/core/sysctl_net_core.c | 6 ++++--
 net/sched/sch_generic.c    | 2 +-
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 716df64fcfa5..b5b92dcd5eea 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5918,7 +5918,7 @@ static int process_backlog(struct napi_struct *napi, int quota)
 		net_rps_action_and_irq_enable(sd);
 	}
 
-	napi->weight = dev_rx_weight;
+	napi->weight = READ_ONCE(dev_rx_weight);
 	while (again) {
 		struct sk_buff *skb;
 
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index 71a13596ea2b..d82ba0c27175 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -240,8 +240,10 @@ static int proc_do_dev_weight(struct ctl_table *table, int write,
 	if (ret != 0)
 		return ret;
 
-	dev_rx_weight = weight_p * dev_weight_rx_bias;
-	dev_tx_weight = weight_p * dev_weight_tx_bias;
+	WRITE_ONCE(dev_rx_weight,
+		   READ_ONCE(weight_p) * READ_ONCE(dev_weight_rx_bias));
+	WRITE_ONCE(dev_tx_weight,
+		   READ_ONCE(weight_p) * READ_ONCE(dev_weight_tx_bias));
 
 	return ret;
 }
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index d47b9689eba6..99b697ad2b98 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -409,7 +409,7 @@ static inline bool qdisc_restart(struct Qdisc *q, int *packets)
 
 void __qdisc_run(struct Qdisc *q)
 {
-	int quota = dev_tx_weight;
+	int quota = READ_ONCE(dev_tx_weight);
 	int packets;
 
 	while (qdisc_restart(q, &packets)) {
-- 
2.30.2