[PATCH net v2 1/2] net: psp: avoid conflicts with skb->decrypted and sk_validate_xmit_skb()

[Daniel Zahka <daniel.zahka@gmail.com>]

PSP conflicts with TLS ULP in its usage of both skb->decrypted and
sk->sk_validate_xmit_skb().

Make PSP mutually exclusive with TLS ULP, the only other user of either
of these. As other users of skb->decrypted come along, they can be added
to sk_has_decrypt_user(). It would make sense to also assert that
sk->sk_validate_xmit_skb() is also NULL in both of these setup paths for
similar future proofing, but the PSP listener/sk_clone() path is still
broken and it could be seen as a regression to not allow rx assoc to run
on a child of a listener socket with PSP tx assoc state.

Include all TCP ULPs in the sk_has_decrypt_user() check, even though TLS
is the only one that conflicts with PSP via the decrypted bit. This is
intentional because PSP was not designed to be used with ULPs. It is
best to close off surface area that may make bugs reachable, until
someone wishes to design and test an actual user of PSP with ULPs.

Fixes: 6b46ca260e22 ("net: psp: add socket security association code")
Signed-off-by: Daniel Zahka <daniel.zahka@gmail.com>
---
 include/net/sock.h | 2 ++
 net/core/sock.c    | 7 +++++++
 net/ipv4/tcp_ulp.c | 4 ++++
 net/psp/psp_sock.c | 4 ++++
 4 files changed, 17 insertions(+)

diff --git a/include/net/sock.h b/include/net/sock.h
index 51185222aac2..60ea55dc1885 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2312,6 +2312,8 @@ static inline void sk_gso_disable(struct sock *sk)
 	sk->sk_route_caps &= ~NETIF_F_GSO_MASK;
 }
 
+bool sk_has_decrypt_user(const struct sock *sk);
+
 static inline int skb_do_copy_data_nocache(struct sock *sk, struct sk_buff *skb,
 					   struct iov_iter *from, char *to,
 					   int copy, int offset)
diff --git a/net/core/sock.c b/net/core/sock.c
index fa60b7494c58..9489d9c47949 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -142,6 +142,7 @@
 
 #include <trace/events/sock.h>
 
+#include <net/psp.h>
 #include <net/tcp.h>
 #include <net/busy_poll.h>
 #include <net/phonet/phonet.h>
@@ -2670,6 +2671,12 @@ void sk_setup_caps(struct sock *sk, struct dst_entry *dst)
 }
 EXPORT_SYMBOL_GPL(sk_setup_caps);
 
+bool sk_has_decrypt_user(const struct sock *sk)
+{
+	return psp_sk_assoc(sk) ||
+	       (sk_is_inet(sk) && inet_csk_has_ulp(sk)); /* for tls */
+}
+
 /*
  *	Simple resource managers for sockets.
  */
diff --git a/net/ipv4/tcp_ulp.c b/net/ipv4/tcp_ulp.c
index 2aa442128630..b58045df101e 100644
--- a/net/ipv4/tcp_ulp.c
+++ b/net/ipv4/tcp_ulp.c
@@ -136,6 +136,10 @@ static int __tcp_set_ulp(struct sock *sk, const struct tcp_ulp_ops *ulp_ops)
 	if (icsk->icsk_ulp_ops)
 		goto out_err;
 
+	err = -EINVAL;
+	if (sk_has_decrypt_user(sk))
+		goto out_err;
+
 	if (sk->sk_socket)
 		clear_bit(SOCK_SUPPORT_ZC, &sk->sk_socket->flags);
 
diff --git a/net/psp/psp_sock.c b/net/psp/psp_sock.c
index 1a2a6b7516b0..e9b53eedf8db 100644
--- a/net/psp/psp_sock.c
+++ b/net/psp/psp_sock.c
@@ -143,6 +143,10 @@ int psp_sock_assoc_set_rx(struct sock *sk, struct psp_assoc *pas,
 		NL_SET_ERR_MSG(extack, "Socket already has PSP state");
 		err = -EBUSY;
 		goto exit_unlock;
+	} else if (sk_has_decrypt_user(sk)) {
+		NL_SET_ERR_MSG(extack, "Socket has incompatible state");
+		err = -EINVAL;
+		goto exit_unlock;
 	}
 
 	refcount_inc(&pas->refcnt);

-- 
2.52.0