netdev - Re: [net] net/tls: Fix to avoid gettig invalid tls record

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Message-ID: <20200212200945.34460c3a@cakuba.hsd1.ca.comcast.net>
Date:   Wed, 12 Feb 2020 20:09:45 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Rohit Maheshwari <rohitm@...lsio.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        linux-crypto@...r.kernel.org
Subject: Re: [net] net/tls: Fix to avoid gettig invalid tls record

On Wed, 12 Feb 2020 12:46:30 +0530, Rohit Maheshwari wrote:
> Current code doesn't check if tcp sequence number is starting from (/after)
> 1st record's start sequnce number. It only checks if seq number is before
> 1st record's end sequnce number. This problem will always be a possibility
> in re-transmit case. If a record which belongs to a requested seq number is
> already deleted, tls_get_record will start looking into list and as per the
> check it will look if seq number is before the end seq of 1st record, which
> will always be true and will return 1st record always, it should in fact
> return NULL. 

I think I see your point, do you observe this problem in practice 
or did you find this through code review?

> diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
> index cd91ad812291..2898517298bf 100644
> --- a/net/tls/tls_device.c
> +++ b/net/tls/tls_device.c
> @@ -602,7 +602,8 @@ struct tls_record_info *tls_get_record(struct tls_offload_context_tx *context,
>  		 */
>  		info = list_first_entry_or_null(&context->records_list,
>  						struct tls_record_info, list);
> -		if (!info)
> +		/* return NULL if seq number even before the 1st entry. */
> +		if (!info || before(seq, info->end_seq - info->len))

Is it not more appropriate to use between() in the actual comparison
below? I feel like with this patch we can get false negatives.

>  			return NULL;
>  		record_sn = context->unacked_record_sn;
>  	}

If you post a v2 please add a Fixes tag and CC maintainers of this code.