netdev - Re: [net-next v5 3/3] net/tls: Remove redundant array allocation.

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Message-Id: <20180723.214109.32924668491950691.davem@davemloft.net>
Date:   Mon, 23 Jul 2018 21:41:09 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     davejwatson@...com
Cc:     vakul.garg@....com, netdev@...r.kernel.org, borisp@...lanox.com,
        aviadye@...lanox.com, doronrk@...com
Subject: Re: [net-next v5 3/3] net/tls: Remove redundant array allocation.

From: Dave Watson <davejwatson@...com>
Date: Mon, 23 Jul 2018 09:35:09 -0700

> I don't think this patch is safe as-is.  sgin_arr is a stack array of
> size MAX_SKB_FRAGS (+ overhead), while my read of skb_cow_data is that
> it walks the whole chain of skbs from skb->next, and can return any
> number of segments.  Therefore we need to heap allocate.  I think I
> copied the IPSEC code here.

Ok I see what you are saying.

So it means that, when a non-NULL sgout is passed into decrypt_skb(),
via decrypt_skb_update(), via tls_sw_recvmsg() it means that it is the
zerocopy case and you know that you only have page frags and no SKB
frag list, right?

I agree with you that this change is therefore incorrect.