linux-kernel - Re: [RFC v3 05/10] iommu: Do not map reserved regions

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:   Tue, 6 Dec 2016 17:36:34 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Eric Auger <eric.auger@...hat.com>, eric.auger.pro@...il.com,
        christoffer.dall@...aro.org, marc.zyngier@....com,
        alex.williamson@...hat.com, will.deacon@....com, joro@...tes.org,
        tglx@...utronix.de, jason@...edaemon.net,
        linux-arm-kernel@...ts.infradead.org
Cc:     kvm@...r.kernel.org, drjones@...hat.com,
        linux-kernel@...r.kernel.org, pranav.sawargaonkar@...il.com,
        iommu@...ts.linux-foundation.org, punit.agrawal@....com,
        diana.craciun@....com
Subject: Re: [RFC v3 05/10] iommu: Do not map reserved regions

On 15/11/16 13:09, Eric Auger wrote:
> As we introduced IOMMU_RESV_NOMAP and IOMMU_RESV_MSI regions,
> let's prevent those new regions from being mapped.
> 
> Signed-off-by: Eric Auger <eric.auger@...hat.com>
> ---
>  drivers/iommu/iommu.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 6ee529f..a4530ad 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -343,6 +343,9 @@ static int iommu_group_create_direct_mappings(struct iommu_group *group,
>  		start = ALIGN(entry->start, pg_size);
>  		end   = ALIGN(entry->start + entry->length, pg_size);
>  
> +		if (entry->prot & IOMMU_RESV_MASK)

This seems to be the only place that this mask is used, and frankly I
think it's less clear than simply "(IOMMU_RESV_NOMAP | IOMMU_RESV_MSI)"
would be, at which point we may as well drop the mask and special value
trickery altogether. Plus, per my previous comment, if it were to be "if
(entry->type != <direct mapped type>)" instead, that's about as obvious
as it can get.

Robin.

> +			continue;
> +
>  		for (addr = start; addr < end; addr += pg_size) {
>  			phys_addr_t phys_addr;
>  
>