linux-kernel - Re: [PATCH v2 1/2] x86/msr: Carry on after a non-"safe" MSR access fails without !panic_on

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:	Sat, 12 Mar 2016 17:02:42 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Paolo Bonzini <pbonzini@...hat.com>,
	xen-devel <Xen-devel@...ts.xen.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KVM list <kvm@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] x86/msr: Carry on after a non-"safe" MSR access
 fails without !panic_on_oops


* Andy Lutomirski <luto@...capital.net> wrote:

> On Thu, Oct 1, 2015 at 12:15 AM, Ingo Molnar <mingo@...nel.org> wrote:
> >
> > * Andy Lutomirski <luto@...capital.net> wrote:
> >
> >> > These could still be open coded in an inlined fashion, like the scheduler usage.
> >>
> >> We could have a raw_rdmsr for those.
> >>
> >> OTOH, I'm still not 100% convinced that this warn-but-don't-die behavior is
> >> worth the effort.  This isn't a frequent source of bugs to my knowledge, and we
> >> don't try to recover from incorrect cr writes, out-of-bounds MMIO, etc, so do we
> >> really gain much by rigging a recovery mechanism for rdmsr and wrmsr failures
> >> for code that doesn't use the _safe variants?
> >
> > It's just the general principle really: don't crash the kernel on bootup. There's
> > few things more user hostile than that.
> >
> > Also, this would maintain the status quo: since we now (accidentally) don't crash
> > the kernel on distro kernels (but silently and unsafely ignore the faulting
> > instruction), we should not regress that behavior (by adding the chance to crash
> > again), but improve upon it.
> 
> Just a heads up: the extable improvements in tip:ras/core make it
> straightforward to get the best of all worlds: explicit failure
> handling (written in C!), no fast path overhead whatsoever, and no new
> garbage in the exception handlers.

I _knew_ I should have merged them into tip:x86/mm, not tip:ras/core ;-)

I had a quick look at your new MSR series and I'm very happy with that direction!

Thanks,

	Ingo