From: Matthew Garrett <mjg@redhat.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: T Makphaibulchoke <tmac@hp.com>,
tglx@linutronix.de, mingo@redhat.com, x86@kernel.org,
akpm@linux-foundation.org, yinghai@kernel.org, tiwai@suse.de,
viro@zeniv.linux.org.uk, aarcange@redhat.com,
tony.luck@intel.com, mgorman@suse.de, weiyang@linux.vnet.ibm.com,
octavian.purdila@intel.com, paul.gortmaker@windriver.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] Fix devmem_is_allowed for below 1MB accesses for an efi machine
Date: Wed, 3 Oct 2012 05:31:17 +0100 [thread overview]
Message-ID: <20121003043116.GA26241@srcf.ucam.org> (raw)
In-Reply-To: <506B6191.6080605@zytor.com>
On Tue, Oct 02, 2012 at 02:50:09PM -0700, H. Peter Anvin wrote:
> That sounds like exactly the opposite of normal /dev/mem behavior... we
> allow access to non-memory resources (which really could do anything if
> misused), but not memory.
>From arch/x86/mm/init.c:
* On x86, access has to be given to the first megabyte of ram because that area
* contains bios code and data regions used by X and dosemu and similar apps.
Limiting this to just RAM would be safer than it currently is. I'm not
convinced that there's any good reason to allow *any* access down there
for EFI systems, though.
--
Matthew Garrett | mjg59@srcf.ucam.org
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WARNING: multiple messages have this Message-ID (diff)
From: Matthew Garrett <mjg@redhat.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: T Makphaibulchoke <tmac@hp.com>,
tglx@linutronix.de, mingo@redhat.com, x86@kernel.org,
akpm@linux-foundation.org, yinghai@kernel.org, tiwai@suse.de,
viro@zeniv.linux.org.uk, aarcange@redhat.com,
tony.luck@intel.com, mgorman@suse.de, weiyang@linux.vnet.ibm.com,
octavian.purdila@intel.com, paul.gortmaker@windriver.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] Fix devmem_is_allowed for below 1MB accesses for an efi machine
Date: Wed, 3 Oct 2012 05:31:17 +0100 [thread overview]
Message-ID: <20121003043116.GA26241@srcf.ucam.org> (raw)
In-Reply-To: <506B6191.6080605@zytor.com>
On Tue, Oct 02, 2012 at 02:50:09PM -0700, H. Peter Anvin wrote:
> That sounds like exactly the opposite of normal /dev/mem behavior... we
> allow access to non-memory resources (which really could do anything if
> misused), but not memory.
>From arch/x86/mm/init.c:
* On x86, access has to be given to the first megabyte of ram because that area
* contains bios code and data regions used by X and dosemu and similar apps.
Limiting this to just RAM would be safer than it currently is. I'm not
convinced that there's any good reason to allow *any* access down there
for EFI systems, though.
--
Matthew Garrett | mjg59@srcf.ucam.org
next prev parent reply other threads:[~2012-10-03 4:32 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-02 21:32 [PATCH] Fix devmem_is_allowed for below 1MB accesses for an efi machine T Makphaibulchoke
2012-10-02 21:32 ` T Makphaibulchoke
2012-10-02 21:50 ` H. Peter Anvin
2012-10-02 21:50 ` H. Peter Anvin
2012-10-03 4:31 ` Matthew Garrett [this message]
2012-10-03 4:31 ` Matthew Garrett
2012-10-03 4:44 ` H. Peter Anvin
2012-10-03 4:44 ` H. Peter Anvin
2012-10-03 5:15 ` Matthew Garrett
2012-10-03 5:15 ` Matthew Garrett
2012-10-03 5:13 ` Thavatchai Makphaibulchoke
2012-10-03 5:13 ` Thavatchai Makphaibulchoke
2012-10-03 5:28 ` Matthew Garrett
2012-10-03 5:28 ` Matthew Garrett
2012-10-03 5:35 ` H. Peter Anvin
2012-10-03 5:35 ` H. Peter Anvin
2012-10-03 5:27 ` H. Peter Anvin
2012-10-03 5:27 ` H. Peter Anvin
[not found] <jQim6-6MC-7@gated-at.bofh.it>
[not found] ` <jQiFt-6UB-13@gated-at.bofh.it>
[not found] ` <jQoUx-33k-3@gated-at.bofh.it>
[not found] ` <jQp4d-37r-3@gated-at.bofh.it>
[not found] ` <jQpxf-3Cv-1@gated-at.bofh.it>
2012-10-04 20:07 ` Randy Wright
2012-10-04 21:06 ` H. Peter Anvin
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