Date: Sat, 9 Aug 2003 13:36:37 -0700
From: "David S. Miller" <davem@redhat.com>
To: Mika =?ISO-8859-1?B?UGVudHRpbOQ=?= <mika.penttila@kolumbus.fi>
Cc: linux-kernel@vger.kernel.org, linux-net@vger.kernel.org
Subject: Re: cryptoapi incorrect struct page usage
Message-Id: <20030809133637.137e8128.davem@redhat.com>
In-Reply-To: <3F355AB0.6@kolumbus.fi>
References: <3F355AB0.6@kolumbus.fi>
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On Sat, 09 Aug 2003 23:33:52 +0300
Mika Penttil? <mika.penttila@kolumbus.fi> wrote:

>         sg[elt].page = virt_to_page(skb->data + offset);
>         sg[elt].offset = (unsigned long)(skb->data + offset) % PAGE_SIZE;
>         sg[elt].length = copy;
> 
> so unpinned pages are passed to cryptoapi. Nothing prevents these pages 
> from being swapped out. Something like get_user_pages() is needed to pin 
> these pages for the duration of crypto operations. Comments?

The page at skb->data was allocated by the skbuff allocation
layer, it has therefore a lifetime the size of the SKB itself.

The crypto API call is finished before we can possibly free up
the SKB, so nothing bad can happen.
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