linux-kernel - Re: [PATCH v2] KVM: SVM: Use kzalloc for sev ioctl interfaces to prevent kernel memory leak.

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Date:   Thu, 19 May 2022 10:08:44 -0700
From:   Peter Gonda <pgonda@...gle.com>
To:     Ashish Kalra <Ashish.Kalra@....com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Joerg Roedel <joro@...tes.org>,
        "Lendacky, Thomas" <Thomas.Lendacky@....com>,
        Borislav Petkov <bp@...en8.de>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andy Nguyen <theflow@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        John Allen <john.allen@....com>, stable@...r.kernel.org,
        Michael Roth <michael.roth@....com>
Subject: Re: [PATCH v2] KVM: SVM: Use kzalloc for sev ioctl interfaces to
 prevent kernel memory leak.

On Mon, May 16, 2022 at 8:43 AM Ashish Kalra <Ashish.Kalra@....com> wrote:
>
> From: Ashish Kalra <ashish.kalra@....com>
>
> For some sev ioctl interfaces, the length parameter that is passed maybe
> less than or equal to SEV_FW_BLOB_MAX_SIZE, but larger than the data
> that PSP firmware returns. In this case, kmalloc will allocate memory
> that is the size of the input rather than the size of the data.
> Since PSP firmware doesn't fully overwrite the allocated buffer, these
> sev ioctl interface may return uninitialized kernel slab memory.
>
> Reported-by: Andy Nguyen <theflow@...gle.com>
> Suggested-by: David Rientjes <rientjes@...gle.com>
> Suggested-by: Peter Gonda <pgonda@...gle.com>
> Cc: kvm@...r.kernel.org
> Cc: stable@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Fixes: eaf78265a4ab3 ("KVM: SVM: Move SEV code to separate file")
> Fixes: 2c07ded06427d ("KVM: SVM: add support for SEV attestation command")
> Fixes: 4cfdd47d6d95a ("KVM: SVM: Add KVM_SEV SEND_START command")
> Fixes: d3d1af85e2c75 ("KVM: SVM: Add KVM_SEND_UPDATE_DATA command")
> Fixes: eba04b20e4861 ("KVM: x86: Account a variety of miscellaneous allocations")
> Signed-off-by: Ashish Kalra <ashish.kalra@....com>

Reviewed-by: Peter Gonda <pgonda@...gle.com>