From: John Fastabend <john.fastabend@gmail.com>
Date: Wed, 3 Nov 2021 13:47:32 -0700
Subject: bpf, sockmap: Use stricter sk state checks in sk_lookup_assign
Patch-mainline: v5.16-rc1
Git-commit: 40a34121ac1dc52ed9cd34a8f4e48e32517a52fd
References: jsc#PED-1377

In order to fix an issue with sockets in TCP sockmap redirect cases we plan
to allow CLOSE state sockets to exist in the sockmap. However, the check in
bpf_sk_lookup_assign() currently only invalidates sockets in the
TCP_ESTABLISHED case relying on the checks on sockmap insert to ensure we
never SOCK_CLOSE state sockets in the map.

To prepare for this change we flip the logic in bpf_sk_lookup_assign() to
explicitly test for the accepted cases. Namely, a tcp socket in TCP_LISTEN
or a udp socket in TCP_CLOSE state. This also makes the code more resilent
to future changes.

Suggested-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/20211103204736.248403-2-john.fastabend@gmail.com
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 include/linux/skmsg.h |   12 ++++++++++++
 net/core/filter.c     |    6 ++++--
 net/core/sock_map.c   |    6 ------
 3 files changed, 16 insertions(+), 8 deletions(-)

--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -507,6 +507,18 @@ static inline bool sk_psock_strp_enabled
 	return !!psock->saved_data_ready;
 }
 
+static inline bool sk_is_tcp(const struct sock *sk)
+{
+	return sk->sk_type == SOCK_STREAM &&
+	       sk->sk_protocol == IPPROTO_TCP;
+}
+
+static inline bool sk_is_udp(const struct sock *sk)
+{
+	return sk->sk_type == SOCK_DGRAM &&
+	       sk->sk_protocol == IPPROTO_UDP;
+}
+
 #if IS_ENABLED(CONFIG_NET_SOCK_MSG)
 
 #define BPF_F_STRPARSER	(1UL << 1)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -10440,8 +10440,10 @@ BPF_CALL_3(bpf_sk_lookup_assign, struct
 		return -EINVAL;
 	if (unlikely(sk && sk_is_refcounted(sk)))
 		return -ESOCKTNOSUPPORT; /* reject non-RCU freed sockets */
-	if (unlikely(sk && sk->sk_state == TCP_ESTABLISHED))
-		return -ESOCKTNOSUPPORT; /* reject connected sockets */
+	if (unlikely(sk && sk_is_tcp(sk) && sk->sk_state != TCP_LISTEN))
+		return -ESOCKTNOSUPPORT; /* only accept TCP socket in LISTEN */
+	if (unlikely(sk && sk_is_udp(sk) && sk->sk_state != TCP_CLOSE))
+		return -ESOCKTNOSUPPORT; /* only accept UDP socket in CLOSE */
 
 	/* Check if socket is suitable for packet L3/L4 protocol */
 	if (sk && sk->sk_protocol != ctx->protocol)
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -511,12 +511,6 @@ static bool sock_map_op_okay(const struc
 	       ops->op == BPF_SOCK_OPS_TCP_LISTEN_CB;
 }
 
-static bool sk_is_tcp(const struct sock *sk)
-{
-	return sk->sk_type == SOCK_STREAM &&
-	       sk->sk_protocol == IPPROTO_TCP;
-}
-
 static bool sock_map_redirect_allowed(const struct sock *sk)
 {
 	if (sk_is_tcp(sk))