linux-kernel - Re: [PATCH] x86: use the right protections for split-up pagetables

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: <499EF77E.8060901@zytor.com>
Date:	Fri, 20 Feb 2009 10:33:34 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	Huang Ying <ying.huang@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Arjan van de Ven <arjan@...radead.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Subject: Re: [PATCH] x86: use the right protections for split-up pagetables

Linus Torvalds wrote:
> 
> The confusion? When it moves the 'ref_prot' bits from the upper level, it 
> doesn't do the right thing for the PAT bit. That bit is special, and moves 
> around depending on level. In the upper levels, it's bit#12, and in the 
> final 4k pte level it's bit#7.
> 

... and in the second level of two-level page tables, it doesn't exist
at all.

Worse, there are errata on some processors (not sure if there are any we
currently don't blacklist) where the PATx bit logic basically gets fed
random data.  Setting up the PAT so that the lower and upper half alias
works around this.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

--
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/