netdev - [PATCH net v2] sctp: Hold sock lock while iterating over address list

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Message-ID: <20251027102541.2320627-2-stefan.wiehler@nokia.com>
Date: Mon, 27 Oct 2025 11:25:42 +0100
From: Stefan Wiehler <stefan.wiehler@...ia.com>
To: Xin Long <lucien.xin@...il.com>,
	"David S . Miller " <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Kuniyuki Iwashima <kuniyu@...gle.com>
Cc: linux-sctp@...r.kernel.org,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Stefan Wiehler <stefan.wiehler@...ia.com>
Subject: [PATCH net v2] sctp: Hold sock lock while iterating over address list

Move address list traversal in inet_assoc_attr_size() under the sock
lock to avoid holding the RCU read lock.

Suggested-by: Xin Long <lucien.xin@...il.com>
Fixes: 8f840e47f190 ("sctp: add the sctp_diag.c file")
Signed-off-by: Stefan Wiehler <stefan.wiehler@...ia.com>
---
V1 -> V2: Add changelog and credit, release sock lock in ENOMEM error path
---
 net/sctp/diag.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/net/sctp/diag.c b/net/sctp/diag.c
index 996c2018f0e6..2cb5693d6af8 100644
--- a/net/sctp/diag.c
+++ b/net/sctp/diag.c
@@ -223,14 +223,15 @@ struct sctp_comm_param {
 	bool net_admin;
 };
 
-static size_t inet_assoc_attr_size(struct sctp_association *asoc)
+static size_t inet_assoc_attr_size(struct sock *sk,
+				   struct sctp_association *asoc)
 {
 	int addrlen = sizeof(struct sockaddr_storage);
 	int addrcnt = 0;
 	struct sctp_sockaddr_entry *laddr;
 
 	list_for_each_entry_rcu(laddr, &asoc->base.bind_addr.address_list,
-				list)
+				list, lockdep_sock_is_held(sk))
 		addrcnt++;
 
 	return	  nla_total_size(sizeof(struct sctp_info))
@@ -256,11 +257,14 @@ static int sctp_sock_dump_one(struct sctp_endpoint *ep, struct sctp_transport *t
 	if (err)
 		return err;
 
-	rep = nlmsg_new(inet_assoc_attr_size(assoc), GFP_KERNEL);
-	if (!rep)
+	lock_sock(sk);
+
+	rep = nlmsg_new(inet_assoc_attr_size(sk, assoc), GFP_KERNEL);
+	if (!rep) {
+		release_sock(sk);
 		return -ENOMEM;
+	}
 
-	lock_sock(sk);
 	if (ep != assoc->ep) {
 		err = -EAGAIN;
 		goto out;
-- 
2.51.0