netdev - [PATCH v1 net 7/8] tls: Use sk_dst_dev_rcu() in get_netdev_for

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Message-ID: <20250911030620.1284754-8-kuniyu@google.com>
Date: Thu, 11 Sep 2025 03:05:35 +0000
From: Kuniyuki Iwashima <kuniyu@...gle.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...gle.com>, 
	Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org, 
	John Fastabend <john.fastabend@...il.com>, Sabrina Dubroca <sd@...asysnail.net>, 
	Ilya Lesokhin <ilyal@...lanox.com>
Subject: [PATCH v1 net 7/8] tls: Use sk_dst_dev_rcu() in get_netdev_for_sock().

get_netdev_for_sock() is called during setsockopt(),
so not under RCU.

Using sk_dst_get(sk)->dev could trigger UAF.

Let's use sk_dst_dev_rcu().

Note that the only ->ndo_sk_get_lower_dev() user is
bond_sk_get_lower_dev(), which uses RCU.

Fixes: e8f69799810c ("net/tls: Add generic NIC offload infrastructure")
Signed-off-by: Kuniyuki Iwashima <kuniyu@...gle.com>
---
Cc: John Fastabend <john.fastabend@...il.com>
Cc: Sabrina Dubroca <sd@...asysnail.net>
Cc: Ilya Lesokhin <ilyal@...lanox.com>
---
 net/tls/tls_device.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
index f672a62a9a52..cacc1709e945 100644
--- a/net/tls/tls_device.c
+++ b/net/tls/tls_device.c
@@ -123,17 +123,17 @@ static void tls_device_queue_ctx_destruction(struct tls_context *ctx)
 /* We assume that the socket is already connected */
 static struct net_device *get_netdev_for_sock(struct sock *sk)
 {
-	struct dst_entry *dst = sk_dst_get(sk);
-	struct net_device *netdev = NULL;
+	struct net_device *dev, *lowest_dev = NULL;
 
-	if (likely(dst)) {
-		netdev = netdev_sk_get_lowest_dev(dst->dev, sk);
-		dev_hold(netdev);
+	rcu_read_lock();
+	dev = sk_dst_dev_rcu(sk);
+	if (likely(dev)) {
+		lowest_dev = netdev_sk_get_lowest_dev(dev, sk);
+		dev_hold(lowest_dev);
 	}
+	rcu_read_unlock();
 
-	dst_release(dst);
-
-	return netdev;
+	return lowest_dev;
 }
 
 static void destroy_record(struct tls_record_info *record)
-- 
2.51.0.384.g4c02a37b29-goog