linux-kernel - Re: [GIT PULL] x86/paravirt for v2.6.33

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] [day] [month] [year] [list]

Date:	Wed, 9 Dec 2009 13:58:33 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickens <hugh@...itas.com>
Subject: Re: [GIT PULL] x86/paravirt for v2.6.33

On Wed, 9 Dec 2009, Jeremy Fitzhardinge wrote:

> On 12/08/09 13:34, Linus Torvalds wrote:
> > I do _not_ want to add any more task_pt_regs() crap, please.
> > 
> > Why? It's wrong for at least vm86 mode (and from kernel system calls).
> >    
> 
> Would the stack frame version work in these cases?

It would "work" in the sense that at least it wouldn't corrupt the "outer" 
stack frame - it would only change the inner one. For vm86 mode, that 
would actually matter (iopl is meaningful), but as Peter also said, I 
don't think we actually allow direct system calls from vm86 mode.

For me it's actually more of a conceptual complaint: I really think 
'task_pt_regs()' is only reliable for ptrace and is simply _wrong_ in 
other situations. On other architectures, you literally need to set up the 
stack _differently_ on the signal handling path - which is what ptrace 
does - than on regular system call paths.

So conceptually, the system call stack layout is simply _different_ than 
the ptrace stack. And I'd hate to have x86 code that teaches people to do 
things that really don't work in general.

			Linus
--
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/