From:   Pietro Borrello <borrello@diag.uniroma1.it>
Date:   Sat, 04 Feb 2023 17:39:20 +0000
Subject: [PATCH net-next v3 1/3] net: add sock_init_data_uid()
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Message-Id: <20230131-tuntap-sk-uid-v3-1-81188b909685@diag.uniroma1.it>
References: <20230131-tuntap-sk-uid-v3-0-81188b909685@diag.uniroma1.it>
In-Reply-To: <20230131-tuntap-sk-uid-v3-0-81188b909685@diag.uniroma1.it>
To:     "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Lorenzo Colitti <lorenzo@google.com>
Cc:     Stephen Hemminger <stephen@networkplumber.org>,
        Cristiano Giuffrida <c.giuffrida@vu.nl>,
        "Bos, H.J." <h.j.bos@vu.nl>, Jakob Koschel <jkl820.git@gmail.com>,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        Pietro Borrello <borrello@diag.uniroma1.it>
Precedence: bulk

Add sock_init_data_uid() to explicitly initialize the socket uid.
To initialise the socket uid, sock_init_data() assumes a the struct
socket* sock is always embedded in a struct socket_alloc, used to
access the corresponding inode uid. This may not be true.
Examples are sockets created in tun_chr_open() and tap_open().

Fixes: 86741ec25462 ("net: core: Add a UID field to struct sock.")
Signed-off-by: Pietro Borrello <borrello@diag.uniroma1.it>
---
 include/net/sock.h |  7 ++++++-
 net/core/sock.c    | 15 ++++++++++++---
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index dcd72e6285b2..937e842dc930 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1956,7 +1956,12 @@ void sk_common_release(struct sock *sk);
  *	Default socket callbacks and setup code
  */
 
-/* Initialise core socket variables */
+/* Initialise core socket variables using an explicit uid. */
+void sock_init_data_uid(struct socket *sock, struct sock *sk, kuid_t uid);
+
+/* Initialise core socket variables.
+ * Assumes struct socket *sock is embedded in a struct socket_alloc.
+ */
 void sock_init_data(struct socket *sock, struct sock *sk);
 
 /*
diff --git a/net/core/sock.c b/net/core/sock.c
index f954d5893e79..9f51ee851a85 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -3379,7 +3379,7 @@ void sk_stop_timer_sync(struct sock *sk, struct timer_list *timer)
 }
 EXPORT_SYMBOL(sk_stop_timer_sync);
 
-void sock_init_data(struct socket *sock, struct sock *sk)
+void sock_init_data_uid(struct socket *sock, struct sock *sk, kuid_t uid)
 {
 	sk_init_common(sk);
 	sk->sk_send_head	=	NULL;
@@ -3399,11 +3399,10 @@ void sock_init_data(struct socket *sock, struct sock *sk)
 		sk->sk_type	=	sock->type;
 		RCU_INIT_POINTER(sk->sk_wq, &sock->wq);
 		sock->sk	=	sk;
-		sk->sk_uid	=	SOCK_INODE(sock)->i_uid;
 	} else {
 		RCU_INIT_POINTER(sk->sk_wq, NULL);
-		sk->sk_uid	=	make_kuid(sock_net(sk)->user_ns, 0);
 	}
+	sk->sk_uid	=	uid;
 
 	rwlock_init(&sk->sk_callback_lock);
 	if (sk->sk_kern_sock)
@@ -3462,6 +3461,16 @@ void sock_init_data(struct socket *sock, struct sock *sk)
 	refcount_set(&sk->sk_refcnt, 1);
 	atomic_set(&sk->sk_drops, 0);
 }
+EXPORT_SYMBOL(sock_init_data_uid);
+
+void sock_init_data(struct socket *sock, struct sock *sk)
+{
+	kuid_t uid = sock ?
+		SOCK_INODE(sock)->i_uid :
+		make_kuid(sock_net(sk)->user_ns, 0);
+
+	sock_init_data_uid(sock, sk, uid);
+}
 EXPORT_SYMBOL(sock_init_data);
 
 void lock_sock_nested(struct sock *sk, int subclass)

-- 
2.25.1