[Qemu-devel] [PATCH] hw/qxl: guest bug on primary create with stride %4 != 0

[Qemu-devel] [PATCH] hw/qxl: guest bug on primary create with stride %4 != 0

[Alon Levy]

Due to usage of pixman for rendering on all spice surfaces we have
pixman's requirement that the stride be word aligned. A guest not
honoring that can crash spice and qemu with it due to failure to create
a surface (in spice-server). Avoid this early on in primary surface
creation and offscreen surface creation.

Recently windows guests got odd width support which triggers a non word
aligned primary surface in 16bit color depth. Off screen surfaces have
always been word aligned, but doesn't hurt to check them here too.

Signed-off-by: Alon Levy <alevy@redhat.com>
---
 hw/qxl.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/hw/qxl.c b/hw/qxl.c
index bd37a83..eaeee76 100644
--- a/hw/qxl.c
+++ b/hw/qxl.c
@@ -459,6 +459,12 @@ static int qxl_track_command(PCIQXLDevice *qxl, struct QXLCommandExt *ext)
                               qxl->ssd.num_surfaces);
             return 1;
         }
+        if (cmd->type == QXL_SURFACE_CMD_CREATE &&
+            (cmd->u.surface_create.stride & 0x03) != 0) {
+            qxl_set_guest_bug(qxl, "QXL_CMD_SURFACE stride = %d %% 4 != 0\n",
+                              cmd->u.surface_create.stride);
+            return 1;
+        }
         qemu_mutex_lock(&qxl->track_lock);
         if (cmd->type == QXL_SURFACE_CMD_CREATE) {
             qxl->guest_surfaces.cmds[id] = ext->cmd.data;
@@ -1382,6 +1388,12 @@ static void qxl_create_guest_primary(PCIQXLDevice *qxl, int loadvm,
     trace_qxl_create_guest_primary_rest(qxl->id, sc->stride, sc->type,
                                         sc->flags);
 
+    if ((surface.stride & 0x3) != 0) {
+        qxl_set_guest_bug(qxl, "primary surface stride = %d %% 4 != 0",
+                          surface.stride);
+        return;
+    }
+
     surface.mouse_mode = true;
     surface.group_id   = MEMSLOT_GROUP_GUEST;
     if (loadvm) {
-- 
1.7.12.1

Re: [Qemu-devel] [PATCH] hw/qxl: guest bug on primary create with stride %4 != 0

[Gerd Hoffmann]

On 10/15/12 14:54, Alon Levy wrote:
> Due to usage of pixman for rendering on all spice surfaces we have
> pixman's requirement that the stride be word aligned. A guest not
> honoring that can crash spice and qemu with it due to failure to create
> a surface (in spice-server). Avoid this early on in primary surface
> creation and offscreen surface creation.

Patch added to spice patch queue.

thanks,
  Gerd