linux-kernel - Re: [PATCH] KVM: x86: remove bogus user-triggerable WARN

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Message-ID: <87lfnv59u8.fsf@nanos.tec.linutronix.de>
Date:   Fri, 20 Mar 2020 16:23:27 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     syzbot+00be5da1d75f1cc95f6b@...kaller.appspotmail.com,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [PATCH] KVM: x86: remove bogus user-triggerable WARN_ON

Thomas Gleixner <tglx@...utronix.de> writes:

> Paolo Bonzini <pbonzini@...hat.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....