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Tsirkin" To: qemu-devel@nongnu.org Cc: Cornelia Huck , Peter Maydell Subject: [PATCH] virtio: stop migrating num_default, validate vring.num on load Message-ID: <3e6a7c403f93acc37af6a6332fdc65049ae218fb.1784894327.git.mst@redhat.com> MIME-Version: 1.0 Content-Disposition: inline X-Mailer: git-send-email 2.51.2.2891.g4157995a80.dirty X-Mutt-Fcc: =sent Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists1p.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.419, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-Zoho-Virus-Status: 1 X-Zoho-AV-Stamp: zmail-av-0.2.10.1.5.2/284.872.57 X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1784894379845158500 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" num_default tracks the allocation size of used_elems, set by virtio_add_queue(). Migrating it via the ringsize subsection is wrong: a migration stream (malicious or simply from a different configuration) can inflate num_default so that virtio_queue_set_num() accepts oversized values, leading to OOB access on the used_elems array. It is not even migrated consistently: a configuration with a smaller num_default could thinkably migrate and work but in the common case of num =3D=3D num_default the value is not actually sent. Stop migrating num_default: make virtio_ringsize_needed() return false so the subsection is never sent, and use VMSTATE_UNUSED to consume the field from old streams without applying it. The destination keeps its local num_default from virtio_add_queue(), which matches the actual allocation. Also validate vring.num against num_default when loading the core virtio state, rejecting streams that supply a queue size larger than the locally allocated maximum. Fixes: 46c5d0823d ("virtio: ring sizes vs. reset") Fixes: 50e5ae4dc3 ("migration/virtio: Remove simple .get/.put use") Cc: Cornelia Huck Cc: Peter Maydell Signed-off-by: Michael S. Tsirkin --- hw/virtio/virtio.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 94ddbfd09f..437c001a04 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -2817,14 +2817,6 @@ static bool virtio_packed_virtqueue_needed(void *opa= que) =20 static bool virtio_ringsize_needed(void *opaque) { - VirtIODevice *vdev =3D opaque; - int i; - - for (i =3D 0; i < VIRTIO_QUEUE_MAX; i++) { - if (vdev->vq[i].vring.num !=3D vdev->vq[i].vring.num_default) { - return true; - } - } return false; } =20 @@ -2913,7 +2905,7 @@ static const VMStateDescription vmstate_ringsize =3D { .version_id =3D 1, .minimum_version_id =3D 1, .fields =3D (const VMStateField[]) { - VMSTATE_UINT32(vring.num_default, struct VirtQueue), + VMSTATE_UNUSED(sizeof(uint32_t)), VMSTATE_END_OF_LIST() } }; @@ -3593,6 +3585,12 @@ virtio_load(VirtIODevice *vdev, QEMUFile *f, int ver= sion_id) =20 for (i =3D 0; i < num; i++) { vdev->vq[i].vring.num =3D qemu_get_be32(f); + if (vdev->vq[i].vring.num > vdev->vq[i].vring.num_default) { + error_report("VQ %d vring.num %u exceeds allocated max %u", + i, vdev->vq[i].vring.num, + vdev->vq[i].vring.num_default); + return -1; + } if (k->has_variable_vring_alignment) { vdev->vq[i].vring.align =3D qemu_get_be32(f); } --=20 MST