linux-kernel - Re: [PATCH] iommu/iova: Sort out rbtree limit

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Message-ID: <20170517140706.GD1912@8bytes.org>
Date:   Wed, 17 May 2017 16:07:06 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Robin Murphy <robin.murphy@....com>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        asierra@...-inc.com, nwatters@...eaurora.org
Subject: Re: [PATCH] iommu/iova: Sort out rbtree limit_pfn handling

On Tue, May 16, 2017 at 12:26:48PM +0100, Robin Murphy wrote:
> When walking the rbtree, the fact that iovad->start_pfn and limit_pfn
> are both inclusive limits creates an ambiguity once limit_pfn reaches
> the bottom of the address space and they overlap. Commit 5016bdb796b3
> ("iommu/iova: Fix underflow bug in __alloc_and_insert_iova_range") fixed
> the worst side-effect of this, that of underflow wraparound leading to
> bogus allocations, but the remaining fallout is that any attempt to
> allocate start_pfn itself erroneously fails.
> 
> The cleanest way to resolve the ambiguity is to simply make limit_pfn an
> exclusive limit when inside the guts of the rbtree. Since we're working
> with PFNs, representing one past the top of the address space is always
> possible without fear of overflow, and elsewhere it just makes life a
> little more straightforward.
> 
> Reported-by: Aaron Sierra <asierra@...-inc.com>
> Signed-off-by: Robin Murphy <robin.murphy@....com>

Applied, thanks.