linux-kernel - Re: BUG: unable to handle kernel paging request from pty

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Message-ID: <20160226181743.GA12735@pd.tnic>
Date:	Fri, 26 Feb 2016 19:17:43 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Peter Hurley <peter@...leysoftware.com>,
	Jiri Slaby <jslaby@...e.cz>,
	Greg KH <gregkh@...uxfoundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	stable <stable@...r.kernel.org>, lwn@....net,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: BUG: unable to handle kernel paging request from pty_write [was:
 Linux 4.4.2]

On Fri, Feb 26, 2016 at 10:05:26AM -0800, Linus Torvalds wrote:
> Of course, if Jiri isn't actually running this on an AMD CPU, that
> theory flies right out the window. But we do have a reported oops on
> the security list that looks totally different in the big picture, but
> shares the exact same "corrupted stack pointer register state
> resulting in crazy instruction pointer, resulting in NX fault"
> behavior in the end.
> 
> In the other case, microcode patchlevel 0x0600081c was fine, and
> 0x06000832 is the one exhibiting the corruption problem.
> 
> I've contacted Robert Święcki (who found the microcode problem) in
> case he wants to weigh in in this thread.. He was talking to some AMD
> people, but I don't know the exactly who.

It most likely is that problem. If Jiri is using the IBS machines -
and from quick look at http://labs.suse.cz/jslaby/bug-968218/gdb_log,
it looks like he is, then they are exactly those boxes with a b0rked
microcode patch. AMD is working on a fix.

-- 
Regards/Gruss,
    Boris.

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