Subject: Re: [PATCH net 1/2] net: hsr: Use the seqnr lock for frames received via interlink port.

From: Lukasz Majewski <[email-masked]>
Date: Wed, 11 Sep 2024 17:46:05 +0200

Hi Sebastian Andrzej,

> syzbot reported that the seqnr_lock is not acquire for frames received
> over the interlink port. In the interlink case a new seqnr is
> generated and assigned to the frame.
> Frames, which are received over the slave port have already a sequence
> number assigned so the lock is not required.
> 
> Acquire the hsr_priv::seqnr_lock during in the invocation of
> hsr_forward_skb() if a packet has been received from the interlink
> port.
> 
> Reported-by: [email-masked]
> Closes:
> https://groups.google.com/g/syzkaller-bugs/c/KppVvGviGg4/m/EItSdCZdBAAJ
> Fixes: 5055cccfc2d1c ("net: hsr: Provide RedBox support (HSR-SAN)")
> Signed-off-by: Sebastian Andrzej Siewior <[email-masked]> ---
>  net/hsr/hsr_slave.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/net/hsr/hsr_slave.c b/net/hsr/hsr_slave.c
> index af6cf64a00e08..464f683e016db 100644
> --- a/net/hsr/hsr_slave.c
> +++ b/net/hsr/hsr_slave.c
> @@ -67,7 +67,16 @@ static rx_handler_result_t hsr_handle_frame(struct
> sk_buff **pskb) skb_set_network_header(skb, ETH_HLEN + HSR_HLEN);
>  	skb_reset_mac_len(skb);
>  
> -	hsr_forward_skb(skb, port);
> +	/* Only the frames received over the interlink port will
> assign a
> +	 * sequence number and require synchronisation vs other
> sender.
> +	 */
> +	if (port->type == HSR_PT_INTERLINK) {
> +		spin_lock_bh(&hsr->seqnr_lock);
> +		hsr_forward_skb(skb, port);
> +		spin_unlock_bh(&hsr->seqnr_lock);
> +	} else {
> +		hsr_forward_skb(skb, port);
> +	}
>  
>  finish_consume:
>  	return RX_HANDLER_CONSUMED;

I've run it through the QEMU + buildroot setup on net-next (SHA1:
bf73478b539b) and no regression was seen.

Thanks for preparing this patch :-)

Reviewed-by: Lukasz Majewski <[email-masked]>
Tested-by: Lukasz Majewski <[email-masked]>

Best regards,

Lukasz Majewski

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