[Qemu-devel] [PULL 6/8] virtio-9p: break device if buffers are misconfigured

[Greg Kurz <groug@kaod.org>]

The 9P protocol is transport agnostic: if the guest misconfigured the
buffers, the best we can do is to set the broken flag on the device.

Signed-off-by: Greg Kurz <groug@kaod.org>
---
 hw/9pfs/9p.c               |  2 +-
 hw/9pfs/9p.h               |  2 +-
 hw/9pfs/virtio-9p-device.c | 40 ++++++++++++++++++++++++++++++++++++----
 hw/9pfs/xen-9p-backend.c   |  3 ++-
 4 files changed, 40 insertions(+), 7 deletions(-)

diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index a0ae98f7ca6f..8e5cac71eb60 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -1664,7 +1664,7 @@ static void v9fs_init_qiov_from_pdu(QEMUIOVector *qiov, V9fsPDU *pdu,
     unsigned int niov;
 
     if (is_write) {
-        pdu->s->transport->init_out_iov_from_pdu(pdu, &iov, &niov);
+        pdu->s->transport->init_out_iov_from_pdu(pdu, &iov, &niov, size + skip);
     } else {
         pdu->s->transport->init_in_iov_from_pdu(pdu, &iov, &niov, size + skip);
     }
diff --git a/hw/9pfs/9p.h b/hw/9pfs/9p.h
index aac1b0b2ce3d..d1cfeaf10e4f 100644
--- a/hw/9pfs/9p.h
+++ b/hw/9pfs/9p.h
@@ -363,7 +363,7 @@ struct V9fsTransport {
     void        (*init_in_iov_from_pdu)(V9fsPDU *pdu, struct iovec **piov,
                                         unsigned int *pniov, size_t size);
     void        (*init_out_iov_from_pdu)(V9fsPDU *pdu, struct iovec **piov,
-                                         unsigned int *pniov);
+                                         unsigned int *pniov, size_t size);
     void        (*push_and_notify)(V9fsPDU *pdu);
 };
 
diff --git a/hw/9pfs/virtio-9p-device.c b/hw/9pfs/virtio-9p-device.c
index 1a68c1622d3a..62650b0a6b99 100644
--- a/hw/9pfs/virtio-9p-device.c
+++ b/hw/9pfs/virtio-9p-device.c
@@ -146,8 +146,16 @@ static ssize_t virtio_pdu_vmarshal(V9fsPDU *pdu, size_t offset,
     V9fsState *s = pdu->s;
     V9fsVirtioState *v = container_of(s, V9fsVirtioState, state);
     VirtQueueElement *elem = v->elems[pdu->idx];
+    ssize_t ret;
 
-    return v9fs_iov_vmarshal(elem->in_sg, elem->in_num, offset, 1, fmt, ap);
+    ret = v9fs_iov_vmarshal(elem->in_sg, elem->in_num, offset, 1, fmt, ap);
+    if (ret < 0) {
+        VirtIODevice *vdev = VIRTIO_DEVICE(v);
+
+        virtio_error(vdev, "Failed to encode VirtFS reply type %d",
+                     pdu->id + 1);
+    }
+    return ret;
 }
 
 static ssize_t virtio_pdu_vunmarshal(V9fsPDU *pdu, size_t offset,
@@ -156,28 +164,52 @@ static ssize_t virtio_pdu_vunmarshal(V9fsPDU *pdu, size_t offset,
     V9fsState *s = pdu->s;
     V9fsVirtioState *v = container_of(s, V9fsVirtioState, state);
     VirtQueueElement *elem = v->elems[pdu->idx];
+    ssize_t ret;
+
+    ret = v9fs_iov_vunmarshal(elem->out_sg, elem->out_num, offset, 1, fmt, ap);
+    if (ret < 0) {
+        VirtIODevice *vdev = VIRTIO_DEVICE(v);
 
-    return v9fs_iov_vunmarshal(elem->out_sg, elem->out_num, offset, 1, fmt, ap);
+        virtio_error(vdev, "Failed to decode VirtFS request type %d", pdu->id);
+    }
+    return ret;
 }
 
-/* The size parameter is used by other transports. Do not drop it. */
 static void virtio_init_in_iov_from_pdu(V9fsPDU *pdu, struct iovec **piov,
                                         unsigned int *pniov, size_t size)
 {
     V9fsState *s = pdu->s;
     V9fsVirtioState *v = container_of(s, V9fsVirtioState, state);
     VirtQueueElement *elem = v->elems[pdu->idx];
+    size_t buf_size = iov_size(elem->in_sg, elem->in_num);
+
+    if (buf_size < size) {
+        VirtIODevice *vdev = VIRTIO_DEVICE(v);
+
+        virtio_error(vdev,
+                     "VirtFS reply type %d needs %zu bytes, buffer has %zu",
+                     pdu->id + 1, size, buf_size);
+    }
 
     *piov = elem->in_sg;
     *pniov = elem->in_num;
 }
 
 static void virtio_init_out_iov_from_pdu(V9fsPDU *pdu, struct iovec **piov,
-                                         unsigned int *pniov)
+                                         unsigned int *pniov, size_t size)
 {
     V9fsState *s = pdu->s;
     V9fsVirtioState *v = container_of(s, V9fsVirtioState, state);
     VirtQueueElement *elem = v->elems[pdu->idx];
+    size_t buf_size = iov_size(elem->out_sg, elem->out_num);
+
+    if (buf_size < size) {
+        VirtIODevice *vdev = VIRTIO_DEVICE(v);
+
+        virtio_error(vdev,
+                     "VirtFS request type %d needs %zu bytes, buffer has %zu",
+                     pdu->id, size, buf_size);
+    }
 
     *piov = elem->out_sg;
     *pniov = elem->out_num;
diff --git a/hw/9pfs/xen-9p-backend.c b/hw/9pfs/xen-9p-backend.c
index 922cc967be63..a82cf817fe45 100644
--- a/hw/9pfs/xen-9p-backend.c
+++ b/hw/9pfs/xen-9p-backend.c
@@ -147,7 +147,8 @@ static ssize_t xen_9pfs_pdu_vunmarshal(V9fsPDU *pdu,
 
 static void xen_9pfs_init_out_iov_from_pdu(V9fsPDU *pdu,
                                            struct iovec **piov,
-                                           unsigned int *pniov)
+                                           unsigned int *pniov,
+                                           size_t size)
 {
     Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
     Xen9pfsRing *ring = &xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings];
-- 
2.7.5