netdev - [PATCH v1 net 4/8] smc: Use sk_dst_dev_rcu() in smc_clc_prfx

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Message-ID: <20250911030620.1284754-5-kuniyu@google.com>
Date: Thu, 11 Sep 2025 03:05:32 +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, 
	"D. Wythe" <alibuda@...ux.alibaba.com>, Dust Li <dust.li@...ux.alibaba.com>, 
	Sidraya Jayagond <sidraya@...ux.ibm.com>, Wenjia Zhang <wenjia@...ux.ibm.com>, 
	Mahanta Jambigi <mjambigi@...ux.ibm.com>, Tony Lu <tonylu@...ux.alibaba.com>, 
	Wen Gu <guwen@...ux.alibaba.com>, Ursula Braun <ubraun@...ux.vnet.ibm.com>
Subject: [PATCH v1 net 4/8] smc: Use sk_dst_dev_rcu() in smc_clc_prfx_match().

smc_clc_prfx_match() is called from smc_listen_work() and
not under RCU nor RTNL.

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

Let's use sk_dst_dev_rcu().

Fixes: a046d57da19f ("smc: CLC handshake (incl. preparation steps)")
Signed-off-by: Kuniyuki Iwashima <kuniyu@...gle.com>
---
Cc: "D. Wythe" <alibuda@...ux.alibaba.com>
Cc: Dust Li <dust.li@...ux.alibaba.com>
Cc: Sidraya Jayagond <sidraya@...ux.ibm.com>
Cc: Wenjia Zhang <wenjia@...ux.ibm.com>
Cc: Mahanta Jambigi <mjambigi@...ux.ibm.com>
Cc: Tony Lu <tonylu@...ux.alibaba.com>
Cc: Wen Gu <guwen@...ux.alibaba.com>
Cc: Ursula Braun <ubraun@...ux.vnet.ibm.com>
---
 net/smc/smc_clc.c | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/net/smc/smc_clc.c b/net/smc/smc_clc.c
index 9aa1d75d3079..5b4fe2c22879 100644
--- a/net/smc/smc_clc.c
+++ b/net/smc/smc_clc.c
@@ -655,26 +655,24 @@ static int smc_clc_prfx_match6_rcu(struct net_device *dev,
 int smc_clc_prfx_match(struct socket *clcsock,
 		       struct smc_clc_msg_proposal_prefix *prop)
 {
-	struct dst_entry *dst = sk_dst_get(clcsock->sk);
+	struct net_device *dev;
 	int rc;
 
-	if (!dst) {
-		rc = -ENOTCONN;
-		goto out;
-	}
-	if (!dst->dev) {
+	rcu_read_lock();
+
+	dev = sk_dst_dev_rcu(clcsock->sk);
+	if (!dev) {
 		rc = -ENODEV;
-		goto out_rel;
+		goto out;
 	}
-	rcu_read_lock();
+
 	if (!prop->ipv6_prefixes_cnt)
-		rc = smc_clc_prfx_match4_rcu(dst->dev, prop);
+		rc = smc_clc_prfx_match4_rcu(dev, prop);
 	else
-		rc = smc_clc_prfx_match6_rcu(dst->dev, prop);
-	rcu_read_unlock();
-out_rel:
-	dst_release(dst);
+		rc = smc_clc_prfx_match6_rcu(dev, prop);
 out:
+	rcu_read_unlock();
+
 	return rc;
 }
 
-- 
2.51.0.384.g4c02a37b29-goog