linux-kernel - Re: [RFC] x86_64: A real proposal for iret-less return to kernel

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]

Date:	Wed, 21 May 2014 14:59:38 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Jiri Kosina <jkosina@...e.cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andi Kleen <andi@...stfloor.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
	Tony Luck <tony.luck@...el.com>
Subject: Re: [RFC] x86_64: A real proposal for iret-less return to kernel

On Wed, May 21, 2014 at 2:55 PM, Borislav Petkov <bp@...en8.de> wrote:
> On Wed, May 21, 2014 at 02:52:55PM -0700, Andy Lutomirski wrote:
>> Why is it a problem if user_mode_vm(regs)?  Conversely, why is sending
>> a signal a remotely reasonable thing to do if !user_mode_vm(regs)?
>
> Let me quote Jiri:
>
> (1) task sends signal to itself
> (2) it acquires sighand->siglock so that it's able to queue the signal
> (3) MCE triggers

...and !user_mode_vm(regs), and hence we're IN_KERNEL, and we should
presumably just panic instead of trying to send a signal.

I missed the IN_KERNEL thing because I didn't realize that ->cs was
copied to struct mce.

--Andy
--
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/