[Qemu-devel] [PATCH v5 0/5] 9pfs: handle transport errors

[Qemu-devel] [PATCH v5 0/5] 9pfs: handle transport errors

[Greg Kurz]

The 9p protocol relies on a reliable transport, but the current code
treats transport errors (ie, failure to marshal or unmarshal) as if
they were coming from the backend. This doesn't make sense: if the
transport failed, we should notify the guest that the transport is
broken and needs to be reset, using transport specific means.

This series modifies both virtio and xen transports to take appropriate
actions when hitting misconfigured buffers.

--
Greg

---

Greg Kurz (4):
      virtio-9p: record element after sanity checks
      virtio-9p: message header is 7-byte long
      virtio-9p: break device if buffers are misconfigured
      9pfs: handle transport errors in pdu_complete()

Stefano Stabellini (1):
      xen-9pfs: disconnect if buffers are misconfigured


 hw/9pfs/9p.c               |   25 ++++++++-----
 hw/9pfs/9p.h               |    7 +++-
 hw/9pfs/virtio-9p-device.c |   51 +++++++++++++++++++++-----
 hw/9pfs/xen-9p-backend.c   |   88 +++++++++++++++++++++++++++++++++-----------
 4 files changed, 129 insertions(+), 42 deletions(-)

[Qemu-devel] [PATCH v5 1/5] virtio-9p: record element after sanity checks

[Greg Kurz]

If the guest sends a malformed request, we end up with a dangling pointer
in V9fsVirtioState. This doesn't seem to cause any bug, but let's remove
this side effect anyway.

Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/9pfs/virtio-9p-device.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/hw/9pfs/virtio-9p-device.c b/hw/9pfs/virtio-9p-device.c
index 245abd8aaef1..3380bfc0c551 100644
--- a/hw/9pfs/virtio-9p-device.c
+++ b/hw/9pfs/virtio-9p-device.c
@@ -61,7 +61,6 @@ static void handle_9p_output(VirtIODevice *vdev, VirtQueue *vq)
         }
         QEMU_BUILD_BUG_ON(sizeof(out) != 7);
 
-        v->elems[pdu->idx] = elem;
         len = iov_to_buf(elem->out_sg, elem->out_num, 0,
                          &out, sizeof(out));
         if (len != sizeof(out)) {
@@ -70,6 +69,8 @@ static void handle_9p_output(VirtIODevice *vdev, VirtQueue *vq)
             goto out_free_req;
         }
 
+        v->elems[pdu->idx] = elem;
+
         pdu_submit(pdu, &out);
     }
 

[Qemu-devel] [PATCH v5 2/5] virtio-9p: message header is 7-byte long

[Greg Kurz]

The 9p spec at http://man.cat-v.org/plan_9/5/intro reads:

 "Each 9P message begins with a four-byte size field specify-
  ing the length in bytes of the complete message including
  the four bytes of the size field itself.  The next byte is
  the message type, one of the constants in the enumeration in
  the include file <fcall.h>.  The next two bytes are an iden-
  tifying tag, described below."

ie, each message starts with a 7-byte long header.

The core 9P code already assumes this pretty much everywhere. This patch
does the following:
- makes the assumption explicit in the common 9p.h header, since it isn't
  related to the transport
- open codes the header size in handle_9p_output() and hardens the sanity
  check on the space needed for the reply message

Signed-off-by: Greg Kurz <groug@kaod.org>
---
 hw/9pfs/9p.h               |    5 +++++
 hw/9pfs/virtio-9p-device.c |    8 +++-----
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/hw/9pfs/9p.h b/hw/9pfs/9p.h
index c886ba78d2ee..aac1b0b2ce3d 100644
--- a/hw/9pfs/9p.h
+++ b/hw/9pfs/9p.h
@@ -124,6 +124,11 @@ typedef struct {
     uint8_t id;
     uint16_t tag_le;
 } QEMU_PACKED P9MsgHeader;
+/* According to the specification, 9p messages start with a 7-byte header.
+ * Since most of the code uses this header size in literal form, we must be
+ * sure this is indeed the case.
+ */
+QEMU_BUILD_BUG_ON(sizeof(P9MsgHeader) != 7);
 
 struct V9fsPDU
 {
diff --git a/hw/9pfs/virtio-9p-device.c b/hw/9pfs/virtio-9p-device.c
index 3380bfc0c551..1a68c1622d3a 100644
--- a/hw/9pfs/virtio-9p-device.c
+++ b/hw/9pfs/virtio-9p-device.c
@@ -53,17 +53,15 @@ static void handle_9p_output(VirtIODevice *vdev, VirtQueue *vq)
             goto out_free_pdu;
         }
 
-        if (elem->in_num == 0) {
+        if (iov_size(elem->in_sg, elem->in_num) < 7) {
             virtio_error(vdev,
                          "The guest sent a VirtFS request without space for "
                          "the reply");
             goto out_free_req;
         }
-        QEMU_BUILD_BUG_ON(sizeof(out) != 7);
 
-        len = iov_to_buf(elem->out_sg, elem->out_num, 0,
-                         &out, sizeof(out));
-        if (len != sizeof(out)) {
+        len = iov_to_buf(elem->out_sg, elem->out_num, 0, &out, 7);
+        if (len != 7) {
             virtio_error(vdev, "The guest sent a malformed VirtFS request: "
                          "header size is %zd, should be 7", len);
             goto out_free_req;

[Qemu-devel] [PATCH v5 3/5] virtio-9p: break device if buffers are misconfigured

[Greg Kurz]

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.

Since virtio_pdu_vmarshal() may be called by several active PDUs, we
check if the transport isn't broken already to avoid printing extra
error messages.

Signed-off-by: Greg Kurz <groug@kaod.org>
---
v5: - use ssize_t variable in virtio_pdu_v[un]marshal()
    - drop remaining vdev->broken check (MST suggested to discuss calling
      virtio_error() when the device is already broken to a separate thread)
---
 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 96d268334865..da0d6da65b45 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];

[Qemu-devel] [PATCH v5 4/5] xen-9pfs: disconnect if buffers are misconfigured

[Greg Kurz]

From: Stefano Stabellini <sstabellini@kernel.org>

Implement xen_9pfs_disconnect by unbinding the event channels. On
xen_9pfs_free, call disconnect if any event channels haven't been
disconnected.

If the frontend misconfigured the buffers set the backend to "Closing"
and disconnect it. Misconfigurations include requesting a read of more
bytes than available on the ring buffer, or claiming to be writing more
data than available on the ring buffer.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
---
Changes:
- fixed some whitespace damages
- xen_9pfs_receive() now returns 0 in case of short read
---
 hw/9pfs/xen-9p-backend.c |   85 +++++++++++++++++++++++++++++++++++-----------
 1 file changed, 64 insertions(+), 21 deletions(-)

diff --git a/hw/9pfs/xen-9p-backend.c b/hw/9pfs/xen-9p-backend.c
index a82cf817fe45..ee87f08926a2 100644
--- a/hw/9pfs/xen-9p-backend.c
+++ b/hw/9pfs/xen-9p-backend.c
@@ -54,6 +54,8 @@ typedef struct Xen9pfsDev {
     Xen9pfsRing *rings;
 } Xen9pfsDev;
 
+static void xen_9pfs_disconnect(struct XenDevice *xendev);
+
 static void xen_9pfs_in_sg(Xen9pfsRing *ring,
                            struct iovec *in_sg,
                            int *num,
@@ -125,10 +127,19 @@ static ssize_t xen_9pfs_pdu_vmarshal(V9fsPDU *pdu,
     Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
     struct iovec in_sg[2];
     int num;
+    ssize_t ret;
 
     xen_9pfs_in_sg(&xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings],
                    in_sg, &num, pdu->idx, ROUND_UP(offset + 128, 512));
-    return v9fs_iov_vmarshal(in_sg, num, offset, 0, fmt, ap);
+
+    ret = v9fs_iov_vmarshal(in_sg, num, offset, 0, fmt, ap);
+    if (ret < 0) {
+        xen_pv_printf(&xen_9pfs->xendev, 0,
+                      "Failed to encode VirtFS request type %d\n", pdu->id + 1);
+        xen_be_set_state(&xen_9pfs->xendev, XenbusStateClosing);
+        xen_9pfs_disconnect(&xen_9pfs->xendev);
+    }
+    return ret;
 }
 
 static ssize_t xen_9pfs_pdu_vunmarshal(V9fsPDU *pdu,
@@ -139,10 +150,19 @@ static ssize_t xen_9pfs_pdu_vunmarshal(V9fsPDU *pdu,
     Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
     struct iovec out_sg[2];
     int num;
+    ssize_t ret;
 
     xen_9pfs_out_sg(&xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings],
                     out_sg, &num, pdu->idx);
-    return v9fs_iov_vunmarshal(out_sg, num, offset, 0, fmt, ap);
+
+    ret = v9fs_iov_vunmarshal(out_sg, num, offset, 0, fmt, ap);
+    if (ret < 0) {
+        xen_pv_printf(&xen_9pfs->xendev, 0,
+                      "Failed to decode VirtFS request type %d\n", pdu->id);
+        xen_be_set_state(&xen_9pfs->xendev, XenbusStateClosing);
+        xen_9pfs_disconnect(&xen_9pfs->xendev);
+    }
+    return ret;
 }
 
 static void xen_9pfs_init_out_iov_from_pdu(V9fsPDU *pdu,
@@ -170,11 +190,22 @@ static void xen_9pfs_init_in_iov_from_pdu(V9fsPDU *pdu,
     Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
     Xen9pfsRing *ring = &xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings];
     int num;
+    size_t buf_size;
 
     g_free(ring->sg);
 
     ring->sg = g_malloc0(sizeof(*ring->sg) * 2);
     xen_9pfs_in_sg(ring, ring->sg, &num, pdu->idx, size);
+
+    buf_size = iov_size(ring->sg, num);
+    if (buf_size  < size) {
+        xen_pv_printf(&xen_9pfs->xendev, 0, "Xen 9pfs request type %d"
+                "needs %zu bytes, buffer has %zu\n", pdu->id, size,
+                buf_size);
+        xen_be_set_state(&xen_9pfs->xendev, XenbusStateClosing);
+        xen_9pfs_disconnect(&xen_9pfs->xendev);
+    }
+
     *piov = ring->sg;
     *pniov = num;
 }
@@ -218,7 +249,7 @@ static int xen_9pfs_init(struct XenDevice *xendev)
 static int xen_9pfs_receive(Xen9pfsRing *ring)
 {
     P9MsgHeader h;
-    RING_IDX cons, prod, masked_prod, masked_cons;
+    RING_IDX cons, prod, masked_prod, masked_cons, queued;
     V9fsPDU *pdu;
 
     if (ring->inprogress) {
@@ -229,8 +260,8 @@ static int xen_9pfs_receive(Xen9pfsRing *ring)
     prod = ring->intf->out_prod;
     xen_rmb();
 
-    if (xen_9pfs_queued(prod, cons, XEN_FLEX_RING_SIZE(ring->ring_order)) <
-        sizeof(h)) {
+    queued = xen_9pfs_queued(prod, cons, XEN_FLEX_RING_SIZE(ring->ring_order));
+    if (queued < sizeof(h)) {
         return 0;
     }
     ring->inprogress = true;
@@ -241,6 +272,9 @@ static int xen_9pfs_receive(Xen9pfsRing *ring)
     xen_9pfs_read_packet((uint8_t *) &h, ring->ring.out, sizeof(h),
                          masked_prod, &masked_cons,
                          XEN_FLEX_RING_SIZE(ring->ring_order));
+    if (queued < le32_to_cpu(h.size_le)) {
+        return 0;
+    }
 
     /* cannot fail, because we only handle one request per ring at a time */
     pdu = pdu_alloc(&ring->priv->state);
@@ -269,15 +303,30 @@ static void xen_9pfs_evtchn_event(void *opaque)
     qemu_bh_schedule(ring->bh);
 }
 
-static int xen_9pfs_free(struct XenDevice *xendev)
+static void xen_9pfs_disconnect(struct XenDevice *xendev)
 {
+    Xen9pfsDev *xen_9pdev = container_of(xendev, Xen9pfsDev, xendev);
     int i;
+
+    for (i = 0; i < xen_9pdev->num_rings; i++) {
+        if (xen_9pdev->rings[i].evtchndev != NULL) {
+            qemu_set_fd_handler(xenevtchn_fd(xen_9pdev->rings[i].evtchndev),
+                    NULL, NULL, NULL);
+            xenevtchn_unbind(xen_9pdev->rings[i].evtchndev,
+                             xen_9pdev->rings[i].local_port);
+            xen_9pdev->rings[i].evtchndev = NULL;
+        }
+    }
+}
+
+static int xen_9pfs_free(struct XenDevice *xendev)
+{
     Xen9pfsDev *xen_9pdev = container_of(xendev, Xen9pfsDev, xendev);
+    int i;
 
-    g_free(xen_9pdev->id);
-    g_free(xen_9pdev->tag);
-    g_free(xen_9pdev->path);
-    g_free(xen_9pdev->security_model);
+    if (xen_9pdev->rings[0].evtchndev != NULL) {
+        xen_9pfs_disconnect(xendev);
+    }
 
     for (i = 0; i < xen_9pdev->num_rings; i++) {
         if (xen_9pdev->rings[i].data != NULL) {
@@ -290,16 +339,15 @@ static int xen_9pfs_free(struct XenDevice *xendev)
                     xen_9pdev->rings[i].intf,
                     1);
         }
-        if (xen_9pdev->rings[i].evtchndev > 0) {
-            qemu_set_fd_handler(xenevtchn_fd(xen_9pdev->rings[i].evtchndev),
-                    NULL, NULL, NULL);
-            xenevtchn_unbind(xen_9pdev->rings[i].evtchndev,
-                             xen_9pdev->rings[i].local_port);
-        }
         if (xen_9pdev->rings[i].bh != NULL) {
             qemu_bh_delete(xen_9pdev->rings[i].bh);
         }
     }
+
+    g_free(xen_9pdev->id);
+    g_free(xen_9pdev->tag);
+    g_free(xen_9pdev->path);
+    g_free(xen_9pdev->security_model);
     g_free(xen_9pdev->rings);
     return 0;
 }
@@ -423,11 +471,6 @@ static void xen_9pfs_alloc(struct XenDevice *xendev)
     xenstore_write_be_int(xendev, "max-ring-page-order", MAX_RING_ORDER);
 }
 
-static void xen_9pfs_disconnect(struct XenDevice *xendev)
-{
-    /* Dynamic hotplug of PV filesystems at runtime is not supported. */
-}
-
 struct XenDevOps xen_9pfs_ops = {
     .size       = sizeof(Xen9pfsDev),
     .flags      = DEVOPS_FLAG_NEED_GNTDEV,

[Qemu-devel] [PATCH v5 5/5] 9pfs: handle transport errors in pdu_complete()

[Greg Kurz]

Contrary to what is written in the comment, a buggy guest can misconfigure
the transport buffers and pdu_marshal() may return an error.  If this ever
happens, it is up to the transport layer to handle the situation (9P is
transport agnostic).

This fixes Coverity issue CID1348518.

Signed-off-by: Greg Kurz <groug@kaod.org>
---
 hw/9pfs/9p.c |   23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index da0d6da65b45..f7871e6f3e5a 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -624,15 +624,11 @@ void pdu_free(V9fsPDU *pdu)
     QLIST_INSERT_HEAD(&s->free_list, pdu, next);
 }
 
-/*
- * We don't do error checking for pdu_marshal/unmarshal here
- * because we always expect to have enough space to encode
- * error details
- */
 static void coroutine_fn pdu_complete(V9fsPDU *pdu, ssize_t len)
 {
     int8_t id = pdu->id + 1; /* Response */
     V9fsState *s = pdu->s;
+    int ret;
 
     if (len < 0) {
         int err = -len;
@@ -644,11 +640,19 @@ static void coroutine_fn pdu_complete(V9fsPDU *pdu, ssize_t len)
             str.data = strerror(err);
             str.size = strlen(str.data);
 
-            len += pdu_marshal(pdu, len, "s", &str);
+            ret = pdu_marshal(pdu, len, "s", &str);
+            if (ret < 0) {
+                goto out_notify;
+            }
+            len += ret;
             id = P9_RERROR;
         }
 
-        len += pdu_marshal(pdu, len, "d", err);
+        ret = pdu_marshal(pdu, len, "d", err);
+        if (ret < 0) {
+            goto out_notify;
+        }
+        len += ret;
 
         if (s->proto_version == V9FS_PROTO_2000L) {
             id = P9_RLERROR;
@@ -657,12 +661,15 @@ static void coroutine_fn pdu_complete(V9fsPDU *pdu, ssize_t len)
     }
 
     /* fill out the header */
-    pdu_marshal(pdu, 0, "dbw", (int32_t)len, id, pdu->tag);
+    if (pdu_marshal(pdu, 0, "dbw", (int32_t)len, id, pdu->tag) < 0) {
+        goto out_notify;
+    }
 
     /* keep these in sync */
     pdu->size = len;
     pdu->id = id;
 
+out_notify:
     pdu->s->transport->push_and_notify(pdu);
 
     /* Now wakeup anybody waiting in flush for this request */

Re: [Qemu-devel] [PATCH v5 2/5] virtio-9p: message header is 7-byte long

[Stefano Stabellini]

On Wed, 28 Jun 2017, Greg Kurz wrote:
> The 9p spec at http://man.cat-v.org/plan_9/5/intro reads:
> 
>  "Each 9P message begins with a four-byte size field specify-
>   ing the length in bytes of the complete message including
>   the four bytes of the size field itself.  The next byte is
>   the message type, one of the constants in the enumeration in
>   the include file <fcall.h>.  The next two bytes are an iden-
>   tifying tag, described below."
> 
> ie, each message starts with a 7-byte long header.
> 
> The core 9P code already assumes this pretty much everywhere. This patch
> does the following:
> - makes the assumption explicit in the common 9p.h header, since it isn't
>   related to the transport
> - open codes the header size in handle_9p_output() and hardens the sanity
>   check on the space needed for the reply message
> 
> Signed-off-by: Greg Kurz <groug@kaod.org>

Acked-by: Stefano Stabellini <sstabellini@kernel.org>


> ---
>  hw/9pfs/9p.h               |    5 +++++
>  hw/9pfs/virtio-9p-device.c |    8 +++-----
>  2 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/9pfs/9p.h b/hw/9pfs/9p.h
> index c886ba78d2ee..aac1b0b2ce3d 100644
> --- a/hw/9pfs/9p.h
> +++ b/hw/9pfs/9p.h
> @@ -124,6 +124,11 @@ typedef struct {
>      uint8_t id;
>      uint16_t tag_le;
>  } QEMU_PACKED P9MsgHeader;
> +/* According to the specification, 9p messages start with a 7-byte header.
> + * Since most of the code uses this header size in literal form, we must be
> + * sure this is indeed the case.
> + */
> +QEMU_BUILD_BUG_ON(sizeof(P9MsgHeader) != 7);
>  
>  struct V9fsPDU
>  {
> diff --git a/hw/9pfs/virtio-9p-device.c b/hw/9pfs/virtio-9p-device.c
> index 3380bfc0c551..1a68c1622d3a 100644
> --- a/hw/9pfs/virtio-9p-device.c
> +++ b/hw/9pfs/virtio-9p-device.c
> @@ -53,17 +53,15 @@ static void handle_9p_output(VirtIODevice *vdev, VirtQueue *vq)
>              goto out_free_pdu;
>          }
>  
> -        if (elem->in_num == 0) {
> +        if (iov_size(elem->in_sg, elem->in_num) < 7) {
>              virtio_error(vdev,
>                           "The guest sent a VirtFS request without space for "
>                           "the reply");
>              goto out_free_req;
>          }
> -        QEMU_BUILD_BUG_ON(sizeof(out) != 7);
>  
> -        len = iov_to_buf(elem->out_sg, elem->out_num, 0,
> -                         &out, sizeof(out));
> -        if (len != sizeof(out)) {
> +        len = iov_to_buf(elem->out_sg, elem->out_num, 0, &out, 7);
> +        if (len != 7) {
>              virtio_error(vdev, "The guest sent a malformed VirtFS request: "
>                           "header size is %zd, should be 7", len);
>              goto out_free_req;
> 

Re: [Qemu-devel] [PATCH v5 5/5] 9pfs: handle transport errors in pdu_complete()

[Stefano Stabellini]

On Wed, 28 Jun 2017, Greg Kurz wrote:
> Contrary to what is written in the comment, a buggy guest can misconfigure
> the transport buffers and pdu_marshal() may return an error.  If this ever
> happens, it is up to the transport layer to handle the situation (9P is
> transport agnostic).
> 
> This fixes Coverity issue CID1348518.
> 
> Signed-off-by: Greg Kurz <groug@kaod.org>

Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>


> ---
>  hw/9pfs/9p.c |   23 +++++++++++++++--------
>  1 file changed, 15 insertions(+), 8 deletions(-)
> 
> diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
> index da0d6da65b45..f7871e6f3e5a 100644
> --- a/hw/9pfs/9p.c
> +++ b/hw/9pfs/9p.c
> @@ -624,15 +624,11 @@ void pdu_free(V9fsPDU *pdu)
>      QLIST_INSERT_HEAD(&s->free_list, pdu, next);
>  }
>  
> -/*
> - * We don't do error checking for pdu_marshal/unmarshal here
> - * because we always expect to have enough space to encode
> - * error details
> - */
>  static void coroutine_fn pdu_complete(V9fsPDU *pdu, ssize_t len)
>  {
>      int8_t id = pdu->id + 1; /* Response */
>      V9fsState *s = pdu->s;
> +    int ret;
>  
>      if (len < 0) {
>          int err = -len;
> @@ -644,11 +640,19 @@ static void coroutine_fn pdu_complete(V9fsPDU *pdu, ssize_t len)
>              str.data = strerror(err);
>              str.size = strlen(str.data);
>  
> -            len += pdu_marshal(pdu, len, "s", &str);
> +            ret = pdu_marshal(pdu, len, "s", &str);
> +            if (ret < 0) {
> +                goto out_notify;
> +            }
> +            len += ret;
>              id = P9_RERROR;
>          }
>  
> -        len += pdu_marshal(pdu, len, "d", err);
> +        ret = pdu_marshal(pdu, len, "d", err);
> +        if (ret < 0) {
> +            goto out_notify;
> +        }
> +        len += ret;
>  
>          if (s->proto_version == V9FS_PROTO_2000L) {
>              id = P9_RLERROR;
> @@ -657,12 +661,15 @@ static void coroutine_fn pdu_complete(V9fsPDU *pdu, ssize_t len)
>      }
>  
>      /* fill out the header */
> -    pdu_marshal(pdu, 0, "dbw", (int32_t)len, id, pdu->tag);
> +    if (pdu_marshal(pdu, 0, "dbw", (int32_t)len, id, pdu->tag) < 0) {
> +        goto out_notify;
> +    }
>  
>      /* keep these in sync */
>      pdu->size = len;
>      pdu->id = id;
>  
> +out_notify:
>      pdu->s->transport->push_and_notify(pdu);
>  
>      /* Now wakeup anybody waiting in flush for this request */
> 

Re: [Qemu-devel] [PATCH v5 3/5] virtio-9p: break device if buffers are misconfigured

[Greg Kurz]

[-- Attachment #1: Type: text/plain, Size: 6074 bytes --]

On Wed, 28 Jun 2017 22:44:30 +0200
Greg Kurz <groug@kaod.org> wrote:

> 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.
> 
> Since virtio_pdu_vmarshal() may be called by several active PDUs, we
> check if the transport isn't broken already to avoid printing extra
> error messages.
> 

Oops, forgot to drop this last sentence... Will do when pushing to my tree.

> Signed-off-by: Greg Kurz <groug@kaod.org>
> ---
> v5: - use ssize_t variable in virtio_pdu_v[un]marshal()
>     - drop remaining vdev->broken check (MST suggested to discuss calling
>       virtio_error() when the device is already broken to a separate thread)
> ---
>  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 96d268334865..da0d6da65b45 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];
> 


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 181 bytes --]

Re: [Qemu-devel] [PATCH v5 2/5] virtio-9p: message header is 7-byte long

[Michael S. Tsirkin]

On Wed, Jun 28, 2017 at 10:44:21PM +0200, Greg Kurz wrote:
> The 9p spec at http://man.cat-v.org/plan_9/5/intro reads:
> 
>  "Each 9P message begins with a four-byte size field specify-
>   ing the length in bytes of the complete message including
>   the four bytes of the size field itself.  The next byte is
>   the message type, one of the constants in the enumeration in
>   the include file <fcall.h>.  The next two bytes are an iden-
>   tifying tag, described below."
> 
> ie, each message starts with a 7-byte long header.
> 
> The core 9P code already assumes this pretty much everywhere. This patch
> does the following:
> - makes the assumption explicit in the common 9p.h header, since it isn't
>   related to the transport
> - open codes the header size in handle_9p_output() and hardens the sanity
>   check on the space needed for the reply message
> 
> Signed-off-by: Greg Kurz <groug@kaod.org>

Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

> ---
>  hw/9pfs/9p.h               |    5 +++++
>  hw/9pfs/virtio-9p-device.c |    8 +++-----
>  2 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/9pfs/9p.h b/hw/9pfs/9p.h
> index c886ba78d2ee..aac1b0b2ce3d 100644
> --- a/hw/9pfs/9p.h
> +++ b/hw/9pfs/9p.h
> @@ -124,6 +124,11 @@ typedef struct {
>      uint8_t id;
>      uint16_t tag_le;
>  } QEMU_PACKED P9MsgHeader;
> +/* According to the specification, 9p messages start with a 7-byte header.
> + * Since most of the code uses this header size in literal form, we must be
> + * sure this is indeed the case.
> + */
> +QEMU_BUILD_BUG_ON(sizeof(P9MsgHeader) != 7);
>  
>  struct V9fsPDU
>  {
> diff --git a/hw/9pfs/virtio-9p-device.c b/hw/9pfs/virtio-9p-device.c
> index 3380bfc0c551..1a68c1622d3a 100644
> --- a/hw/9pfs/virtio-9p-device.c
> +++ b/hw/9pfs/virtio-9p-device.c
> @@ -53,17 +53,15 @@ static void handle_9p_output(VirtIODevice *vdev, VirtQueue *vq)
>              goto out_free_pdu;
>          }
>  
> -        if (elem->in_num == 0) {
> +        if (iov_size(elem->in_sg, elem->in_num) < 7) {
>              virtio_error(vdev,
>                           "The guest sent a VirtFS request without space for "
>                           "the reply");
>              goto out_free_req;
>          }
> -        QEMU_BUILD_BUG_ON(sizeof(out) != 7);
>  
> -        len = iov_to_buf(elem->out_sg, elem->out_num, 0,
> -                         &out, sizeof(out));
> -        if (len != sizeof(out)) {
> +        len = iov_to_buf(elem->out_sg, elem->out_num, 0, &out, 7);
> +        if (len != 7) {
>              virtio_error(vdev, "The guest sent a malformed VirtFS request: "
>                           "header size is %zd, should be 7", len);
>              goto out_free_req;

Re: [Qemu-devel] [PATCH v5 3/5] virtio-9p: break device if buffers are misconfigured

[Michael S. Tsirkin]

On Wed, Jun 28, 2017 at 10:44:30PM +0200, Greg Kurz wrote:
> 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.
> 
> Since virtio_pdu_vmarshal() may be called by several active PDUs, we
> check if the transport isn't broken already to avoid printing extra
> error messages.
> 
> Signed-off-by: Greg Kurz <groug@kaod.org>

Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

> ---
> v5: - use ssize_t variable in virtio_pdu_v[un]marshal()
>     - drop remaining vdev->broken check (MST suggested to discuss calling
>       virtio_error() when the device is already broken to a separate thread)
> ---
>  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 96d268334865..da0d6da65b45 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];

Re: [Qemu-devel] [PATCH v5 3/5] virtio-9p: break device if buffers are misconfigured

[Greg Kurz]

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On Fri, 30 Jun 2017 02:33:22 +0300
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Wed, Jun 28, 2017 at 10:44:30PM +0200, Greg Kurz wrote:
> > 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.
> > 
> > Since virtio_pdu_vmarshal() may be called by several active PDUs, we
> > check if the transport isn't broken already to avoid printing extra
> > error messages.
> > 
> > Signed-off-by: Greg Kurz <groug@kaod.org>  
> 
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> 

Oops, I've already sent a pull request and it got merged.

Thanks for the Reviewed-by's anyway.

> > ---
> > v5: - use ssize_t variable in virtio_pdu_v[un]marshal()
> >     - drop remaining vdev->broken check (MST suggested to discuss calling
> >       virtio_error() when the device is already broken to a separate thread)
> > ---
> >  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 96d268334865..da0d6da65b45 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];  


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