linux-kernel - Re: [PATCH v4 13/14] rxrpc: Prepare to remove VLA usage for SKCIPHER_REQUEST_ON

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Date:   Thu, 12 Jul 2018 23:05:20 +0100
From:   David Howells <dhowells@...hat.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     dhowells@...hat.com, Kees Cook <keescook@...omium.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Eric Biggers <ebiggers@...gle.com>,
        Alasdair Kergon <agk@...hat.com>,
        Giovanni Cabiddu <giovanni.cabiddu@...el.com>,
        Lars Persson <larper@...s.com>,
        Mike Snitzer <snitzer@...hat.com>,
        Rabin Vincent <rabinv@...s.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        "David S. Miller" <davem@...emloft.net>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>, qat-linux@...el.com,
        dm-devel@...hat.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 13/14] rxrpc: Prepare to remove VLA usage for SKCIPHER_REQUEST_ON_STACK

Arnd Bergmann <arnd@...db.de> wrote:

> From what I can tell, neither of the two are called in atomic context, so
> you should be able to use a GFP_KERNEL allocation.

You need to be careful doing that since the allocation might happen in the AFS
writeback path.  I use GFP_NOIO or GFP_NOFS in rxkad.c and skb_cow_data() uses
GFP_ATOMIC - though we should have single ownership of the packet at this
point.

David