linux-kernel - Re: [PATCH] Kconfig: Make config Filter access to /dev/mem default y

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]

Message-ID: <20100415145940.243723b7@lxorguk.ukuu.org.uk>
Date:	Thu, 15 Apr 2010 14:59:40 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Michal Svoboda <michal.svoboda@...nts.felk.cvut.cz>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Kconfig: Make config Filter access to /dev/mem default
 y

On Thu, 15 Apr 2010 15:41:53 +0200
Michal Svoboda <michal.svoboda@...nts.felk.cvut.cz> wrote:

> Jiri Kosina wrote:
> > Access to /dev/mem being filtered in PAT obviously applies only to x86. 
> > 
> > Architectures which don't do such filtering in their respective 
> > phys_mem_access_prot_allowed() still need this option.
> 
> So why not use it for all archs uniformly? Is PAT filtering better in
> some ways? 

PAT is an x86 specific hardware feature. The x86 processors can set per
page caching properties as with some other CPU designs. In the x86 case
all references to the page must have the same cache settings so the PAT
implementation has to filter /dev/mem access to avoid machine check
errors.

It's not implemented as a security feature, its a side effect of the
hardware requirements on that CPU range.

Alan
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/