[PATCH 4.19 19/56] net: Fix data-races around weight_p and dev_weight_[rt]x_bias.

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit bf955b5ab8f6f7b0632cdef8e36b14e4f6e77829 ]

While reading weight_p, it can be changed concurrently.  Thus, we need
to add READ_ONCE() to its reader.

Also, dev_[rt]x_weight can be read/written at the same time.  So, we
need to use READ_ONCE() and WRITE_ONCE() for its access.  Moreover, to
use the same weight_p while changing dev_[rt]x_weight, we add a mutex
in proc_do_dev_weight().

Fixes: 3d48b53fb2ae ("net: dev_weight: TX/RX orthogonality")
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/core/dev.c             |  2 +-
 net/core/sysctl_net_core.c | 15 +++++++++------
 net/sched/sch_generic.c    |  2 +-
 3 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 42f6ff8b9703c..6ee4390863fbe 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5851,7 +5851,7 @@ 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 0a0bf80623658..d7e39167ceca0 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -231,14 +231,17 @@ static int set_default_qdisc(struct ctl_table *table, int write,
 static int proc_do_dev_weight(struct ctl_table *table, int write,
 			   void __user *buffer, size_t *lenp, loff_t *ppos)
 {
-	int ret;
+	static DEFINE_MUTEX(dev_weight_mutex);
+	int ret, weight;
 
+	mutex_lock(&dev_weight_mutex);
 	ret = proc_dointvec(table, write, buffer, lenp, ppos);
-	if (ret != 0)
-		return ret;
-
-	dev_rx_weight = weight_p * dev_weight_rx_bias;
-	dev_tx_weight = weight_p * dev_weight_tx_bias;
+	if (!ret && write) {
+		weight = READ_ONCE(weight_p);
+		WRITE_ONCE(dev_rx_weight, weight * dev_weight_rx_bias);
+		WRITE_ONCE(dev_tx_weight, weight * dev_weight_tx_bias);
+	}
+	mutex_unlock(&dev_weight_mutex);
 
 	return ret;
 }
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index cad2586c34734..c966dacf1130b 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -397,7 +397,7 @@ 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)) {
-- 
2.35.1