Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <20190710201244.25195-1-brijesh.singh@amd.com> <20190710201244.25195-6-brijesh.singh@amd.com>
In-Reply-To: <20190710201244.25195-6-brijesh.singh@amd.com>
From:   Peter Gonda <pgonda@google.com>
Date:   Thu, 14 Nov 2019 13:02:28 -0800
Message-ID: <CAMkAt6rwbq6XC_K64arBUmqsTzSWk7Zoazq-YcqLvjc-rmW8BA@mail.gmail.com>
Subject: Re: [PATCH v3 05/11] KVM: SVM: Add KVM_SEV_RECEIVE_UPDATE_DATA command
To:     "Singh, Brijesh" <brijesh.singh@amd.com>
Cc:     "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Joerg Roedel <joro@8bytes.org>, Borislav Petkov <bp@suse.de>,
        "Lendacky, Thomas" <Thomas.Lendacky@amd.com>,
        "x86@kernel.org" <x86@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

> +
> +       /* Check if we are crossing the page boundry */
> +       offset = params.guest_uaddr & (PAGE_SIZE - 1);
> +       if ((params.guest_len + offset > PAGE_SIZE))
> +               return -EINVAL;

Just curious spec only says that "System physical of the guest memory
region. Must be 16 B aligned with the C-bit set." and "Length of guest
memory region. Must be a multiple of 16 B and no more than 16 kB". Why
do we want to avoid crossing a page boundary?

Also is there an overflow concern in the conditional because
params.guest_len is not checked before this?

> +
> +       data = kzalloc(sizeof(*data), GFP_KERNEL);
> +       if (!data)
> +               return -ENOMEM;
> +
> +       hdr = psp_copy_user_blob(params.hdr_uaddr, params.hdr_len);
> +       if (IS_ERR(hdr)) {
> +               ret = PTR_ERR(hdr);
> +               goto e_free;
> +       }
> +