netdev - Re: [PATCH net 0/9] rxrpc: Fix use of skb_cow

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Message-Id: <20190822.121207.731320146177703787.davem@davemloft.net>
Date:   Thu, 22 Aug 2019 12:12:07 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     dhowells@...hat.com
Cc:     netdev@...r.kernel.org, linux-afs@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 0/9] rxrpc: Fix use of skb_cow_data()

From: David Howells <dhowells@...hat.com>
Date: Thu, 22 Aug 2019 13:22:33 +0100

> Here's a series of patches that fixes the use of skb_cow_data() in rxrpc.
> The problem is that skb_cow_data() indirectly requires that the maximum
> usage count on an sk_buff be 1, and it may generate an assertion failure in
> pskb_expand_head() if not.

It sounds like you are effectively doing a late unshare when you have to
do in-place encryption.

Why don't you just do an skb_unshare() at the beginning when you know that
you'll need to do that?