linux-kernel - Re: [PATCH] tpm: Detach page allocation from tpm

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 25 Sep 2019 10:03:46 -0400
From:   James Bottomley <James.Bottomley@...senPartnership.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        linux-integrity@...r.kernel.org
Cc:     Mimi Zohar <zohar@...ux.ibm.com>,
        Jerry Snitselaar <jsnitsel@...hat.com>,
        Sumit Garg <sumit.garg@...aro.org>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        Peter Huewe <peterhuewe@....de>,
        Jason Gunthorpe <jgg@...pe.ca>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tpm: Detach page allocation from tpm_buf

On Wed, 2019-09-25 at 16:48 +0300, Jarkko Sakkinen wrote:
[...]
> +	data_page = alloc_page(GFP_HIGHUSER);
> +	if (!data_page)
> +		return -ENOMEM;
> +
> +	data_ptr = kmap(data_page);

I don't think this is such a good idea.  On 64 bit it's no different
from GFP_KERNEL and on 32 bit where we do have highmem, kmap space is
at a premium, so doing a highmem allocation + kmap is more wasteful of
resources than simply doing GFP_KERNEL.  In general, you should only do
GFP_HIGHMEM if the page is going to be mostly used by userspace, which
really isn't the case here.

James