From: Ingo Molnar <mingo@elte.hu>
To: Jamie Lokier <jamie@shareable.org>
Cc: linux-kernel@vger.kernel.org, Andi Kleen <ak@suse.de>,
Andrew Morton <akpm@osdl.org>, Linus Torvalds <torvalds@osdl.org>
Subject: Re: Do x86 NX and AMD prefetch check cause page fault infinite loop?
Date: Fri, 2 Jul 2004 09:15:12 +0200 [thread overview]
Message-ID: <20040702071512.GA11709@elte.hu> (raw)
In-Reply-To: <20040701150430.GB5114@mail.shareable.org>
* Jamie Lokier <jamie@shareable.org> wrote:
> > - if (pmd_val(*pmd) & _PAGE_NX)
> > - printk(KERN_CRIT "kernel tried to access NX-protected page - exploit attempt? (uid: %d)\n", current->uid);
> > - }
> > - }
> > -#endif
> > + if (nx_enabled && (error_code & 16))
> > + printk(KERN_CRIT "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n", current->uid);
>
> According to AMD's manual, bit 4 of error_code means the fault was due
> to an instruction fetch. It doesn't imply that it's an NX-protected
> page: it might be a page not present fault instead. (The manual
> doesn't spell that out, it just says the bit is set when it's an
> instruction fetch).
you are right, it doesnt say it's an NX related fault.
I'll test this out and send a delta patch.
Ingo
next prev parent reply other threads:[~2004-07-02 12:17 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-06-30 1:38 Do x86 NX and AMD prefetch check cause page fault infinite loop? Jamie Lokier
2004-06-30 5:50 ` Ingo Molnar
2004-06-30 14:21 ` Jamie Lokier
2004-06-30 14:38 ` Jamie Lokier
2004-07-01 1:48 ` Jamie Lokier
2004-07-01 6:32 ` Ingo Molnar
2004-07-01 15:04 ` Jamie Lokier
2004-07-02 7:15 ` Ingo Molnar [this message]
2004-07-02 8:50 ` [patch] i386 nx prefetch fix & cleanups, 2.6.7-mm5 Ingo Molnar
2004-06-30 6:10 ` Do x86 NX and AMD prefetch check cause page fault infinite loop? Denis Vlasenko
2004-06-30 14:23 ` Jamie Lokier
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