linux-kernel - Re: [PATCH] fix size checks for mmap() on /proc/bus/pci files (updated)

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Date:	Wed, 10 Nov 2010 10:44:34 -0800
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Martin Wilck <martin.wilck@...fujitsu.com>
Cc:	gerhard.wichert@...fujitsu.com, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH] fix size checks for mmap() on /proc/bus/pci files
 (updated)

On Wed, 10 Nov 2010 11:03:21 +0100
Martin Wilck <martin.wilck@...fujitsu.com> wrote:

> The checks for valid mmaps of PCI resources made
> through /proc/bus/pci files that were introduced in
> 9eff02e2042f96fb2aedd02e032eca1c5333d767 have several problems:
> 
> 1. mmap() calls on /proc/bus/pci files are made with real file
> offsets > 0, whereas under /sys/bus/pci/devices, the start of the
> resource corresponds to offset 0. This may lead to false negatives in
> pci_mmap_fits(), which implicitly assumes the /sys/bus/pci/devices
> layout.
> 
> 2. The loop in proc_bus_pci_mmap doesn't skip empty resouces. This
> leads to false positives, because pci_mmap_fits() doesn't treat empty
> resources correctly (the calculated size is 1 <<
> (8*sizeof(resource_size_t)-PAGE_SHIFT) in this case!).
> 
> 3. If a user maps resources with BAR > 0, pci_mmap_fits will emit
> bogus WARNINGS for the first resources that don't fit until the
> correct one is found.
> 
> On many controllers the first 2-4 BARs are used, and the others are
> empty. In this case, an mmap attempt will first fail on the non-empty
> BARs (including the "right" BAR because of 1.) and emit bogus
> WARNINGS because of 3., and finally succeed on the first empty BAR
> because of 2. This is certainly not the intended behaviour.
> 
> This patch addresses all 3 issues.
> Updated with an enum type for the additional parameter for
> pci_mmap_fits().
> 
> Signed-off-by: Martin Wilck <martin.wilck@...fujitsu.com>

Thanks Martin, I'll push this into my for-linus branch for 2.6.37; may
as well cc: stable as well, since this is a long standing bug.

-- 
Jesse Barnes, Intel Open Source Technology Center
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