netdev - Re: [PATCH net-next v13 08/19] net: psp: add socket security association code

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Message-ID: <CANn89i+GxfOvKg2TVGGsnibK0SGT_sdcbMB0K-hje=yQac3fhA@mail.gmail.com>
Date: Wed, 17 Sep 2025 21:18:49 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: Daniel Zahka <daniel.zahka@...il.com>
Cc: Donald Hunter <donald.hunter@...il.com>, Jakub Kicinski <kuba@...nel.org>, 
	"David S. Miller" <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Jonathan Corbet <corbet@....net>, Andrew Lunn <andrew+netdev@...n.ch>, 
	Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>, Tariq Toukan <tariqt@...dia.com>, 
	Boris Pismenny <borisp@...dia.com>, Kuniyuki Iwashima <kuniyu@...gle.com>, 
	Willem de Bruijn <willemb@...gle.com>, David Ahern <dsahern@...nel.org>, 
	Neal Cardwell <ncardwell@...gle.com>, Patrisious Haddad <phaddad@...dia.com>, Raed Salem <raeds@...dia.com>, 
	Jianbo Liu <jianbol@...dia.com>, Dragos Tatulea <dtatulea@...dia.com>, 
	Rahul Rameshbabu <rrameshbabu@...dia.com>, Stanislav Fomichev <sdf@...ichev.me>, 
	Toke Høiland-Jørgensen <toke@...hat.com>, 
	Alexander Lobakin <aleksander.lobakin@...el.com>, Kiran Kella <kiran.kella@...adcom.com>, 
	Jacob Keller <jacob.e.keller@...el.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v13 08/19] net: psp: add socket security
 association code

On Tue, Sep 16, 2025 at 5:10 PM Daniel Zahka <daniel.zahka@...il.com> wrote:
>
> From: Jakub Kicinski <kuba@...nel.org>
>
> Add the ability to install PSP Rx and Tx crypto keys on TCP
> connections. Netlink ops are provided for both operations.
> Rx side combines allocating a new Rx key and installing it
> on the socket. Theoretically these are separate actions,
> but in practice they will always be used one after the
> other. We can add distinct "alloc" and "install" ops later.
>
> Reviewed-by: Willem de Bruijn <willemb@...gle.com>
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> Co-developed-by: Daniel Zahka <daniel.zahka@...il.com>
> Signed-off-by: Daniel Zahka <daniel.zahka@...il.com>
> ---
>

> +
> +static inline struct psp_assoc *psp_sk_get_assoc_rcu(struct sock *sk)

nit : const struct sock *sk;

> +{
> +       struct inet_timewait_sock *tw;
> +       struct psp_assoc *pas;
> +       int state;
> +
> +       state = 1 << READ_ONCE(sk->sk_state);

nit: Not sure why you need flags, you could later compare with TCP_NEW_SYN_RECV
and


> +       if (!sk_is_inet(sk) || state & TCPF_NEW_SYN_RECV)
> +               return NULL;
> +
> +       tw = inet_twsk(sk);

It seems strange to use inet_twsk() helper without knowing it is a tw socket.
(fine today, but strange)

pas = state == TCP_TIME_WAIT ? rcu_dereference(inet_twsk(sk)->psp_assoc) :


> +       pas = state & TCPF_TIME_WAIT ? rcu_dereference(tw->psp_assoc) :
> +                                      rcu_dereference(sk->psp_assoc);
> +       return pas;
>  }
>

...

> +
> +struct psp_dev *psp_dev_get_for_sock(struct sock *sk)
> +{
> +       struct dst_entry *dst;
> +       struct psp_dev *psd;
> +
> +       dst = sk_dst_get(sk);
> +       if (!dst)
> +               return NULL;
> +
> +       rcu_read_lock();
> +       psd = rcu_dereference(dst->dev->psp_dev);
> +       if (psd && !psp_dev_tryget(psd))
> +               psd = NULL;
> +       rcu_read_unlock();
> +
> +       dst_release(dst);
> +
> +       return psd;
> +}

I would rather not use sk_dst_get() and risk UAF later on dst->dev->psp_dev;

I would instead use dst_dev_rcu() and __sk_dst_get().

{
   struct psp_dev *psd = NULL;
   struct dst_entry *dst;

   rcu_read_lock();
   dst  = __sk_dst_get(sk);
   if (!dst)
       goto unlock;
   psd = rcu_dereference(dst_dev_rcu(dst)->psp_dev);
   if (psd && !psp_dev_tryget(psd))
           psd = NULL;
unlock:
   rcu_read_unlock();
   return psd;
}

This can be done later, I can provide a patch myself after this series
is merged.

Reviewed-by: Eric Dumazet <edumazet@...gle.com>