net: psp: avoid conflicts with skb->decrypted and sk_validate_xmit_skb()

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>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20260915-psp-ktls-fix-v2-1-0eedc3b148ec@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 2 insertions, 0 deletions

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)