linux-kernel - Re: [RFC PATCH v1 01/10] KVM: SVM: Add KVM_SEV SEND

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Message-ID: <20190429163602.GE2324@zn.tnic>
Date:   Mon, 29 Apr 2019 18:36:02 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Singh, Brijesh" <brijesh.singh@....com>
Cc:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "qemu-devel@...gnu.org" <qemu-devel@...gnu.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        "Lendacky, Thomas" <Thomas.Lendacky@....com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v1 01/10] KVM: SVM: Add KVM_SEV SEND_START command

On Mon, Apr 29, 2019 at 03:01:24PM +0000, Singh, Brijesh wrote:
> Practically I don't see any reason why caller would do that but
> theoretically it can. If we cache the len then we also need to consider
> adding another flag to hint whether userspace ever requested length.
> e.g an application can compute the length of session blob by looking at
> the API version and spec and may never query the length.
> 
> > I mean I'm still thinking defensively here but maybe the only thing that
> > would happen here with a bigger buffer is if the kmalloc() would fail,
> > leading to eventual failure of the migration.
> > 
> > If the code limits the allocation to some sane max length, the migration
> > won't fail even if userspace gives it too big values...

So what about this? Limiting to a sane length...

-- 
Regards/Gruss,
    Boris.

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