From: Paolo Bonzini <pbonzini@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: syzbot+00be5da1d75f1cc95f6b@syzkaller.appspotmail.com,
Sean Christopherson <sean.j.christopherson@intel.com>
Subject: Re: [PATCH] KVM: x86: remove bogus user-triggerable WARN_ON
Date: Fri, 20 Mar 2020 18:47:43 +0100 [thread overview]
Message-ID: <ef15a35b-3e69-7922-ceda-4a4867054a44@redhat.com> (raw)
In-Reply-To: <87lfnv59u8.fsf@nanos.tec.linutronix.de>
On 20/03/20 16:23, Thomas Gleixner wrote:
> Thomas Gleixner <tglx@linutronix.de> writes:
>
>> Paolo Bonzini <pbonzini@redhat.com> writes:
>>> The WARN_ON is essentially comparing a user-provided value with 0. It is
>>> trivial to trigger it just by passing garbage to KVM_SET_CLOCK. Guests
>>> can break if you do so, but if it hurts when you do like this just do not
>>> do it.
>>
>> Yes, it's a user provided value and it's completely unchecked. If that
>> value is bogus then the guest will go sideways because timekeeping is
>> completely busted. At least you should explain WHY you don't care.
>
> Or why it does not matter....
I can change the commit message to "Guests can break if you do so, but
the same applies to every KVM_SET_* ioctl". It's impossible to be sure
that userspace doesn't ever send a bogus KVM_SET_CLOCK and later
rectifies it with the right value.
Paolo
next prev parent reply other threads:[~2020-03-20 17:47 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-19 17:43 Paolo Bonzini
2020-03-19 17:52 ` Sean Christopherson
2020-03-20 15:22 ` Thomas Gleixner
2020-03-20 15:23 ` Thomas Gleixner
2020-03-20 17:47 ` Paolo Bonzini [this message]
2020-03-20 18:18 ` Thomas Gleixner
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