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From 88fd47b4c3a1a272d7e21ba0e7358e0a4e9ecf88 Mon Sep 17 00:00:00 2001
From: Dr. David Alan Gilbert (git) <dgilbert@redhat.com>
Date: Mon, 30 Jun 2014 11:10:01 +0200
Subject: [PATCH] Allow mismatched virtio config-len

RH-Author: Dr. David Alan Gilbert (git) <dgilbert@redhat.com>
Message-id: <1404126601-23992-2-git-send-email-dgilbert@redhat.com>
Patchwork-id: 59407
O-Subject: [RHEL-7.0.z qemu-kvm PATCH 1/1] Allow mismatched virtio config-len
Bugzilla: 1095782
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Juan Quintela <quintela@redhat.com>
RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Commit 'virtio: validate config_len on load' restricted config_len
loaded from the wire to match the config_len that the device had.

Unfortunately, there are cases where this isn't true, the one
we found it on was the wce addition in virtio-blk.

Allow mismatched config-lengths:
   *) If the version on the wire is shorter then fine
   *) If the version on the wire is longer, load what we have space
      for and skip the rest.

(This is mst@redhat.com's rework of what I originally posted)

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 2f5732e9648fcddc8759a8fd25c0b41a38352be6)
---
 hw/virtio/virtio.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 hw/virtio/virtio.c |   16 +++++++++++-----
 1 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 44309c2..132b5af 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -886,12 +886,18 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f)
         return -1;
     }
     config_len = qemu_get_be32(f);
-    if (config_len != vdev->config_len) {
-        error_report("Unexpected config length 0x%x. Expected 0x%zx",
-                     config_len, vdev->config_len);
-        return -1;
+
+    /*
+     * There are cases where the incoming config can be bigger or smaller
+     * than what we have; so load what we have space for, and skip
+     * any excess that's in the stream.
+     */
+    qemu_get_buffer(f, vdev->config, MIN(config_len, vdev->config_len));
+
+    while (config_len > vdev->config_len) {
+        qemu_get_byte(f);
+        config_len--;
     }
-    qemu_get_buffer(f, vdev->config, vdev->config_len);
 
     num = qemu_get_be32(f);
 
-- 
1.7.1