Subject: Re: [PATCH net-ipsec v2] xfrm: replay: Fix ESN wrap around for GSO

From: Leon Romanovsky <[email-masked]>
Date: Wed, 28 Sep 2022 09:18:07 +0300

On Tue, Sep 27, 2022 at 02:59:50PM +0200, Christian Langrock wrote:
> When using GSO it can happen that the wrong seq_hi is used for the last
> packets before the wrap around. This can lead to double usage of a
> sequence number. To avoid this, we should serialize this last GSO
> packet.
> 
> Fixes: d7dbefc45cf5 ("xfrm: Add xfrm_replay_overflow functions for...")
> Signed-off-by: Christian Langrock <[email-masked]>
> ---
>  include/net/xfrm.h     |  1 +
>  net/xfrm/xfrm_output.c |  2 +-
>  net/xfrm/xfrm_replay.c | 33 +++++++++++++++++++++++++++++++++
>  3 files changed, 35 insertions(+), 1 deletion(-)
> 
> diff --git a/include/net/xfrm.h b/include/net/xfrm.h
> index 6e8fa98f786f..49d6d974f493 100644
> --- a/include/net/xfrm.h
> +++ b/include/net/xfrm.h
> @@ -1749,6 +1749,7 @@ void xfrm_replay_advance(struct xfrm_state *x, __be32 net_seq);
>  int xfrm_replay_check(struct xfrm_state *x, struct sk_buff *skb, __be32 net_seq);
>  void xfrm_replay_notify(struct xfrm_state *x, int event);
>  int xfrm_replay_overflow(struct xfrm_state *x, struct sk_buff *skb);
> +int xfrm_replay_overflow_check(struct xfrm_state *x, struct sk_buff *skb);
>  int xfrm_replay_recheck(struct xfrm_state *x, struct sk_buff *skb, __be32 net_seq);
>  
>  static inline int xfrm_aevent_is_on(struct net *net)
> diff --git a/net/xfrm/xfrm_output.c b/net/xfrm/xfrm_output.c
> index 9a5e79a38c67..c470a68d9c88 100644
> --- a/net/xfrm/xfrm_output.c
> +++ b/net/xfrm/xfrm_output.c
> @@ -738,7 +738,7 @@ int xfrm_output(struct sock *sk, struct sk_buff *skb)
>  		skb->encapsulation = 1;
>  
>  		if (skb_is_gso(skb)) {
> -			if (skb->inner_protocol)
> +			if (skb->inner_protocol || xfrm_replay_overflow_check(x, skb))
>  				return xfrm_output_gso(net, sk, skb);
>  
>  			skb_shinfo(skb)->gso_type |= SKB_GSO_ESP;
> diff --git a/net/xfrm/xfrm_replay.c b/net/xfrm/xfrm_replay.c
> index 9277d81b344c..991cfc7a091d 100644
> --- a/net/xfrm/xfrm_replay.c
> +++ b/net/xfrm/xfrm_replay.c
> @@ -750,6 +750,34 @@ int xfrm_replay_overflow(struct xfrm_state *x, struct sk_buff *skb)
>  
>  	return xfrm_replay_overflow_offload(x, skb);
>  }
> +
> +static bool xfrm_replay_overflow_check_offload_esn(struct xfrm_state *x, struct sk_buff *skb)
> +{
> +	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
> +	__u32 oseq = replay_esn->oseq;
> +	bool ret = false;
> +
> +	/* We assume that this function is called with
> +	 * skb_is_gso(skb) == true
> +	 */
> +
> +	if (x->type->flags & XFRM_TYPE_REPLAY_PROT) {
> +		oseq = oseq + 1 + skb_shinfo(skb)->gso_segs;
> +		if (unlikely(oseq < replay_esn->oseq))
> +			ret = true;

return true;

> +	}
> +
> +	return ret;

return false;

> +}
> +
> +bool xfrm_replay_overflow_check(struct xfrm_state *x, struct sk_buff *skb)
> +{
> +	if (x->repl_mode == XFRM_REPLAY_MODE_ESN)
> +		return xfrm_replay_overflow_check_offload_esn(x, skb);
> +
> +	return false;
> +}

I still think that functions above should be merged into one. This is
called only if xfrm_dev_offload_ok() success -> in crypto offload path.

Thanks

> +
>  #else
>  int xfrm_replay_overflow(struct xfrm_state *x, struct sk_buff *skb)
>  {
> @@ -764,6 +792,11 @@ int xfrm_replay_overflow(struct xfrm_state *x, struct sk_buff *skb)
>  
>  	return __xfrm_replay_overflow(x, skb);
>  }
> +
> +int xfrm_replay_overflow_check(struct xfrm_state *x, struct sk_buff *skb)

int -> bool

> +{
> +	return 0;
> +}
>  #endif
>  
>  int xfrm_init_replay(struct xfrm_state *x)
> -- 
> 2.37.1.223.g6a475b71f8
>