netdev - [Patch bpf 1/3] skmsg: introduce sk_psock_get

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Date:   Fri, 24 Sep 2021 15:05:05 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     netdev@...r.kernel.org
Cc:     bpf@...r.kernel.org, Cong Wang <cong.wang@...edance.com>,
        John Fastabend <john.fastabend@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jakub Sitnicki <jakub@...udflare.com>,
        Lorenz Bauer <lmb@...udflare.com>
Subject: [Patch bpf 1/3] skmsg: introduce sk_psock_get_checked()

From: Cong Wang <cong.wang@...edance.com>

Although we have sk_psock_get(), it assumes the psock
retrieved from sk_user_data is for sockmap, this is not
sufficient if we call it outside of sockmap, for example,
reuseport_array.

Fortunately sock_map_psock_get_checked() is more strict
and checks for sock_map_close before using psock. So we can
refactor it and rename it to sk_psock_get_checked(), which
can be safely called outside of sockmap.

Cc: John Fastabend <john.fastabend@...il.com>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: Jakub Sitnicki <jakub@...udflare.com>
Cc: Lorenz Bauer <lmb@...udflare.com>
Signed-off-by: Cong Wang <cong.wang@...edance.com>
---
 include/linux/skmsg.h | 20 ++++++++++++++++++++
 net/core/sock_map.c   | 22 +---------------------
 2 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index 14ab0c0bc924..d47097f2c8c0 100644
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -452,6 +452,26 @@ static inline struct sk_psock *sk_psock_get(struct sock *sk)
 	return psock;
 }
 
+static inline struct sk_psock *sk_psock_get_checked(struct sock *sk)
+{
+	struct sk_psock *psock;
+
+	rcu_read_lock();
+	psock = sk_psock(sk);
+	if (psock) {
+		if (sk->sk_prot->close != sock_map_close) {
+			psock = ERR_PTR(-EBUSY);
+			goto out;
+		}
+
+		if (!refcount_inc_not_zero(&psock->refcnt))
+			psock = ERR_PTR(-EBUSY);
+	}
+out:
+	rcu_read_unlock();
+	return psock;
+}
+
 void sk_psock_drop(struct sock *sk, struct sk_psock *psock);
 
 static inline void sk_psock_put(struct sock *sk, struct sk_psock *psock)
diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index e252b8ec2b85..6612bb0b95b5 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -191,26 +191,6 @@ static int sock_map_init_proto(struct sock *sk, struct sk_psock *psock)
 	return sk->sk_prot->psock_update_sk_prot(sk, psock, false);
 }
 
-static struct sk_psock *sock_map_psock_get_checked(struct sock *sk)
-{
-	struct sk_psock *psock;
-
-	rcu_read_lock();
-	psock = sk_psock(sk);
-	if (psock) {
-		if (sk->sk_prot->close != sock_map_close) {
-			psock = ERR_PTR(-EBUSY);
-			goto out;
-		}
-
-		if (!refcount_inc_not_zero(&psock->refcnt))
-			psock = ERR_PTR(-EBUSY);
-	}
-out:
-	rcu_read_unlock();
-	return psock;
-}
-
 static int sock_map_link(struct bpf_map *map, struct sock *sk)
 {
 	struct sk_psock_progs *progs = sock_map_progs(map);
@@ -255,7 +235,7 @@ static int sock_map_link(struct bpf_map *map, struct sock *sk)
 		}
 	}
 
-	psock = sock_map_psock_get_checked(sk);
+	psock = sk_psock_get_checked(sk);
 	if (IS_ERR(psock)) {
 		ret = PTR_ERR(psock);
 		goto out_progs;
-- 
2.30.2