From: Paolo Bonzini <pbonzini@redhat.com>
To: Andy Lutomirski <luto@amacapital.net>,
Linus Torvalds <torvalds@linux-foundation.org>
Cc: KVM list <kvm@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>, X86 ML <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
xen-devel <Xen-devel@lists.xen.org>,
Borislav Petkov <bp@alien8.de>,
Andrew Morton <akpm@linux-foundation.org>,
Arjan van de Ven <arjan@linux.intel.com>
Subject: Re: [PATCH v3 3/5] x86/paravirt: Add paravirt_{read, write}_msr
Date: Tue, 15 Mar 2016 09:49:26 +0100 [thread overview]
Message-ID: <56E7CC96.7080301__40636.1511945308$1458031900$gmane$org@redhat.com> (raw)
In-Reply-To: <CALCETrWYmJdOeHqjR6-Uyqiyym35DOjFpsB1xhgTHO_JB==EMA@mail.gmail.com>
On 14/03/2016 18:02, Andy Lutomirski wrote:
> On Mon, Mar 14, 2016 at 9:58 AM, Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
>>
>> On Mar 14, 2016 9:53 AM, "Andy Lutomirski" <luto@amacapital.net> wrote:
>>>
>>> Can you clarify? KVM uses the native version, and the native version
>>> only oopses with this series applied if panic_on_oops is set.
>>
>> Can we please remove that idiocy?
>>
>> There is no reason to panic whatsoever. Seriously. What's the upside of that
>> logic?
>
> I imagine that people who set panic_on_oops want their systems to stop
> running user code if something happens that could corrupt the state or
> if there's any sign that user code is trying some non-deterministic
> exploit. So I'm guessing that they'd want this type of "the kernel
> screwed up -- abort" to actually result in a panic.
>
> As a concrete, although somewhat silly, example, suppose that a write
> to MSR_SYSENTER_STACK fails. If that happened, then user code could
> subsequently try to take over the kernel by evil manipulation of TF
> and/or perf.
>
> I'd be okay with removing this too, though, since arranging for MSR
> access to fail seems unlikely as an exploit vector.
>
> Borislav: SUSE actually uses panic_on_oops, right? What's their goal?
RHEL also does, and it's mostly to trap kernel page faults before they
do more damage such as filesystem corruption. The debug kernel has
panic_on_oops=0, while the production kernel has panic_on_oops=1.
Paolo
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next prev parent reply other threads:[~2016-03-15 8:49 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1457723023.git.luto@kernel.org>
2016-03-11 19:06 ` [PATCH v3 1/5] x86/paravirt: Add _safe to the read_msr and write_msr PV hooks Andy Lutomirski
2016-03-11 19:06 ` [PATCH v3 2/5] x86/msr: Carry on after a non-"safe" MSR access fails without !panic_on_oops Andy Lutomirski
2016-03-11 19:06 ` [PATCH v3 3/5] x86/paravirt: Add paravirt_{read, write}_msr Andy Lutomirski
2016-03-11 19:06 ` [PATCH v3 4/5] x86/paravirt: Make "unsafe" MSR accesses unsafe even if PARAVIRT=y Andy Lutomirski
2016-03-11 19:06 ` [PATCH v3 5/5] x86/msr: Set the return value to zero when native_rdmsr_safe fails Andy Lutomirski
[not found] ` <35f2f107e0d85473a0e66c08f93d571a9c72b7fc.1457723023.git.luto@kernel.org>
2016-03-12 15:31 ` [PATCH v3 2/5] x86/msr: Carry on after a non-"safe" MSR access fails without !panic_on_oops Ingo Molnar
2016-03-12 15:36 ` Ingo Molnar
[not found] ` <20160312153615.GB17873@gmail.com>
2016-03-12 17:32 ` Andy Lutomirski
[not found] ` <c7fb2aafd8a5885e9c333957abef9e29b691098e.1457723023.git.luto@kernel.org>
2016-03-14 14:02 ` [PATCH v3 3/5] x86/paravirt: Add paravirt_{read, write}_msr Paolo Bonzini
[not found] ` <56E6C492.5060308@redhat.com>
2016-03-14 16:53 ` Andy Lutomirski
2016-03-14 16:58 ` Linus Torvalds
2016-03-14 17:02 ` Andy Lutomirski
[not found] ` <CALCETrWYmJdOeHqjR6-Uyqiyym35DOjFpsB1xhgTHO_JB==EMA@mail.gmail.com>
2016-03-15 8:49 ` Paolo Bonzini [this message]
2016-03-15 8:56 ` Paolo Bonzini
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