linux-kernel - Re: [PATCH v3 1/2] tpm: Use GFP_KERNEL for allocating struct tpm

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Date:   Fri, 11 Oct 2019 09:03:50 -0700
From:   James Bottomley <jejb@...ux.ibm.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     linux-integrity@...r.kernel.org, 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 v3 1/2] tpm: Use GFP_KERNEL for allocating struct tpm_buf

On Thu, 2019-10-10 at 00:36 +0300, Jarkko Sakkinen wrote:
> On Mon, Oct 07, 2019 at 12:12:08PM -0700, James Bottomley wrote:
> > From: James Bottomley <James.Bottomley@...senPartnership.com>
> > Subject: [PATCH] tpm: use GFP kernel for tpm_buf allocations
> > 
> > The current code uses GFP_HIGHMEM, which is wrong because
> > GFP_HIGHMEM (on 32 bit systems) is memory ordinarily inaccessible
> > to the kernel and should only be used for allocations affecting
> > userspace.  In order to make highmem visible to the kernel on 32
> > bit it has to be kmapped, which consumes valuable entries in the
> > kmap region.  Since the tpm_buf is only ever used in the kernel,
> > switch to using a GFP_KERNEL allocation so as not to waste kmap
> > space on 32 bits.
> > 
> > Fixes: a74f8b36352e (tpm: introduce tpm_buf)
> > Signed-off-by: James Bottomley <James.Bottomley@...senPartnership.c
> > om>
> 
> Pushed to master branch.

Thanks.  0day spotted a problem with the use of free_page() so I've
sent a v2.

James