File CVE-2014-3615-qemu-ab9509cc.patch of Package xen.529

Subject: spice: make sure we don't overflow ssd->buf
From: Gerd Hoffmann kraxel@redhat.com Wed Sep 3 15:50:08 2014 +0200
Date: Fri Sep 5 12:19:50 2014 +0200:
Git: ab9509cceabef28071e41bdfa073083859c949a7

Related spice-only bug.  We have a fixed 16 MB buffer here, being
presented to the spice-server as qxl video memory in case spice is
used with a non-qxl card.  It's also used with qxl in vga mode.

When using display resolutions requiring more than 16 MB of memory we
are going to overflow that buffer.  In theory the guest can write,
indirectly via spice-server.  The spice-server clears the memory after
setting a new video mode though, triggering a segfault in the overflow
case, so qemu crashes before the guest has a chance to do something
evil.

Fix that by switching to dynamic allocation for the buffer.

CVE-2014-3615

Cc: qemu-stable@nongnu.org
Cc: secalert@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Index: xen-4.4.1-testing/tools/qemu-xen-dir-remote/ui/spice-display.c
===================================================================
--- xen-4.4.1-testing.orig/tools/qemu-xen-dir-remote/ui/spice-display.c
+++ xen-4.4.1-testing/tools/qemu-xen-dir-remote/ui/spice-display.c
@@ -308,11 +308,23 @@ void qemu_spice_create_host_memslot(Simp
 void qemu_spice_create_host_primary(SimpleSpiceDisplay *ssd)
 {
     QXLDevSurfaceCreate surface;
+    uint64_t surface_size;
 
     memset(&surface, 0, sizeof(surface));
 
-    dprint(1, "%s: %dx%d\n", __FUNCTION__,
-           surface_width(ssd->ds), surface_height(ssd->ds));
+    surface_size = (uint64_t) surface_width(ssd->ds) *
+        surface_height(ssd->ds) * 4;
+    assert(surface_size > 0);
+    assert(surface_size < INT_MAX);
+    if (ssd->bufsize < surface_size) {
+        ssd->bufsize = surface_size;
+        g_free(ssd->buf);
+        ssd->buf = g_malloc(ssd->bufsize);
+    }
+
+    dprint(1, "%s/%d: %ux%u (size %" PRIu64 "/%d)\n", __func__, ssd->qxl.id,
+           surface_width(ssd->ds), surface_height(ssd->ds),
+           surface_size, ssd->bufsize);
 
     surface.format     = SPICE_SURFACE_FMT_32_xRGB;
     surface.width      = surface_width(ssd->ds);
@@ -343,8 +355,6 @@ void qemu_spice_display_init_common(Simp
     if (ssd->num_surfaces == 0) {
         ssd->num_surfaces = 1024;
     }
-    ssd->bufsize = (16 * 1024 * 1024);
-    ssd->buf = g_malloc(ssd->bufsize);
 }
 
 /* display listener callbacks */
@@ -462,7 +472,7 @@ static void interface_get_init_info(QXLI
     info->num_memslots = NUM_MEMSLOTS;
     info->num_memslots_groups = NUM_MEMSLOTS_GROUPS;
     info->internal_groupslot_id = 0;
-    info->qxl_ram_size = ssd->bufsize;
+    info->qxl_ram_size = 16 * 1024 * 1024;
     info->n_surfaces = ssd->num_surfaces;
 }