From: Thomas Gleixner <tglx@linutronix.de>
To: Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <sean.j.christopherson@intel.com>
Cc: syzbot <syzbot+00be5da1d75f1cc95f6b@syzkaller.appspotmail.com>,
bp@alien8.de, hpa@zytor.com, jmattson@google.com,
joro@8bytes.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, mingo@redhat.com,
rkrcmar@redhat.com, syzkaller-bugs@googlegroups.com,
vkuznets@redhat.com, wanpengli@tencent.com, x86@kernel.org
Subject: Re: WARNING in vcpu_enter_guest
Date: Fri, 20 Mar 2020 01:18:05 +0100 [thread overview]
Message-ID: <87k13f516q.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <cd32ee6d-f30d-b221-8126-cf995ffca52e@redhat.com>
Paolo Bonzini <pbonzini@redhat.com> writes:
> On 19/03/20 18:39, Sean Christopherson wrote:
>>> Yep. I worked through logic/math, mostly to gain a wee bit of knowledge
>>> about the clock stuff, and it's sound. The KVM_SET_CLOCK from syzkaller
>>> is simply making time go backwards.
>> Actually, would it make sense to return -EINVAL for KVM_SET_CLOCK if the
>> user tries to make kvmclock_offset go backwards?
>
> No, it is possible to do that depending on the clock setup on the live
> migration source. You could cause the warning anyway by setting the
> clock to a very high (signed) value so that kernel_ns + kvmclock_offset
> overflows.
If that overflow happens, then the original and the new host have an
uptime difference in the range of >200 hundreds of years. Very realistic
scenario...
Of course this can happen if you feed crap into the interface, but do
you really think that forwarding all crap to a guest is the right thing
to do?
As we all know the hypervisor orchestration stuff is perfect and would
never feed crap into the kernel which happily proliferates that crap to
the guest...
Seriously??
Thanks,
tglx
next prev parent reply other threads:[~2020-03-20 0:18 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-29 8:20 WARNING in vcpu_enter_guest syzbot
2020-03-19 10:35 ` syzbot
2020-03-19 14:49 ` Sean Christopherson
2020-03-19 15:14 ` Paolo Bonzini
2020-03-19 17:35 ` Sean Christopherson
2020-03-19 17:39 ` Sean Christopherson
2020-03-19 17:44 ` Paolo Bonzini
2020-03-20 0:18 ` Thomas Gleixner [this message]
2020-03-20 10:33 ` Paolo Bonzini
2020-03-20 13:33 ` Thomas Gleixner
2020-03-22 3:31 ` syzbot
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87k13f516q.fsf@nanos.tec.linutronix.de \
--to=tglx@linutronix.de \
--cc=bp@alien8.de \
--cc=hpa@zytor.com \
--cc=jmattson@google.com \
--cc=joro@8bytes.org \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=pbonzini@redhat.com \
--cc=rkrcmar@redhat.com \
--cc=sean.j.christopherson@intel.com \
--cc=syzbot+00be5da1d75f1cc95f6b@syzkaller.appspotmail.com \
--cc=syzkaller-bugs@googlegroups.com \
--cc=vkuznets@redhat.com \
--cc=wanpengli@tencent.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox