From: Matthieu Buffet <matthieu@buffet.re>
Date: Tue, 9 Jun 2026 21:15:10 +0000 (+0200)
Subject: landlock: Fix unmarked concurrent access to socket family
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0ce4243509d1580349dd0d50624036d6b097e958;p=thirdparty%2Fkernel%2Flinux.git

landlock: Fix unmarked concurrent access to socket family

Socket family is read (twice) in a context where the socket is not
locked, so another thread can setsockopt(IPV6_ADDRFORM) to write it
concurrently. Add needed READ_ONCE() annotation.

Use the proper macro to access __sk_common.skc_family like everywhere
else.

Fixes: fff69fb03dde ("landlock: Support network rules with TCP bind and connect")
Signed-off-by: Matthieu Buffet <matthieu@buffet.re>
Link: https://patch.msgid.link/20260609211511.85630-1-matthieu@buffet.re
Link: https://patch.msgid.link/20260609211511.85630-2-matthieu@buffet.re
[mic: Squash two patches, move variable to ease backport, fix comment
formatting]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
---

diff --git a/security/landlock/net.c b/security/landlock/net.c
index a38bdfcffc22..4ee4002a8f56 100644
--- a/security/landlock/net.c
+++ b/security/landlock/net.c
@@ -46,6 +46,7 @@ static int current_check_access_socket(struct socket *const sock,
 				       const int addrlen,
 				       access_mask_t access_request)
 {
+	unsigned short sock_family;
 	__be16 port;
 	struct layer_access_masks layer_masks = {};
 	const struct landlock_rule *rule;
@@ -66,6 +67,12 @@ static int current_check_access_socket(struct socket *const sock,
 	if (addrlen < offsetofend(typeof(*address), sa_family))
 		return -EINVAL;
 
+	/*
+	 * The socket is not locked, so sk_family can change concurrently due to
+	 * e.g. setsockopt(IPV6_ADDRFORM).
+	 */
+	sock_family = READ_ONCE(sock->sk->sk_family);
+
 	switch (address->sa_family) {
 	case AF_UNSPEC:
 		if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP) {
@@ -102,7 +109,7 @@ static int current_check_access_socket(struct socket *const sock,
 			 * these checks, but it is safer to return a proper
 			 * error and test consistency thanks to kselftest.
 			 */
-			if (sock->sk->__sk_common.skc_family == AF_INET) {
+			if (sock_family == AF_INET) {
 				const struct sockaddr_in *const sockaddr =
 					(struct sockaddr_in *)address;
 
@@ -180,7 +187,7 @@ static int current_check_access_socket(struct socket *const sock,
 	 * check, but it is safer to return a proper error and test
 	 * consistency thanks to kselftest.
 	 */
-	if (address->sa_family != sock->sk->__sk_common.skc_family &&
+	if (address->sa_family != sock_family &&
 	    address->sa_family != AF_UNSPEC)
 		return -EINVAL;