[PATCH v5.15-v6.1 2/2] tls: Use __sk_dst_get() and dst_dev_rcu() in get_netdev_for_sock().

[Keerthana K]

From: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>

[ Upstream commit c65f27b9c3be2269918e1cbad6d8884741f835c5 ]

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_get() and 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@xxxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reviewed-by: Sabrina Dubroca <sd@xxxxxxxxxxxxxxx>
Link: https://patch.msgid.link/20250916214758.650211-6-kuniyu@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
[ Keerthana: Backport to v5.15-v6.1 ]
Signed-off-by: Keerthana K <keerthana.kalyanasundaram@xxxxxxxxxxxx>
---
 net/tls/tls_device.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
index c51377a15..e79bce6db 100644
--- a/net/tls/tls_device.c
+++ b/net/tls/tls_device.c
@@ -125,17 +125,19 @@ 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;
+	struct dst_entry *dst;
 
-	if (likely(dst)) {
-		netdev = netdev_sk_get_lowest_dev(dst->dev, sk);
-		dev_hold(netdev);
+	rcu_read_lock();
+	dst = __sk_dst_get(sk);
+	dev = dst ? dst_dev_rcu(dst) : NULL;
+	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)
-- 
2.43.7