File CVE-2016-9921-qemuu-display-cirrus_vga-divide-by-zero-in-cirrus_do_copy.patch of Package xen.11298

References: bsc#1015169 CVE-2016-9921 CVE-2016-9922

Subject: display: cirrus: check vga bits per pixel(bpp) value
From: Prasad J Pandit pjp@fedoraproject.org Tue Oct 18 13:15:17 2016 +0530
Date: Mon Dec 5 11:01:55 2016 +0100:
Git: 4299b90e9ba9ce5ca9024572804ba751aa1a7e70

In Cirrus CLGD 54xx VGA Emulator, if cirrus graphics mode is VGA,
'cirrus_get_bpp' returns zero(0), which could lead to a divide
by zero error in while copying pixel data. The same could occur
via blit pitch values. Add check to avoid it.

Reported-by: Huawei PSIRT <psirt@huawei.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Message-id: 1476776717-24807-1-git-send-email-ppandit@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

Index: xen-4.5.5-testing/tools/qemu-xen-dir-remote/hw/display/cirrus_vga.c
===================================================================
--- xen-4.5.5-testing.orig/tools/qemu-xen-dir-remote/hw/display/cirrus_vga.c
+++ xen-4.5.5-testing/tools/qemu-xen-dir-remote/hw/display/cirrus_vga.c
@@ -710,7 +710,7 @@ static int cirrus_bitblt_videotovideo_pa
                                             s->cirrus_addr_mask));
 }
 
-static void cirrus_do_copy(CirrusVGAState *s, int dst, int src, int w, int h)
+static int cirrus_do_copy(CirrusVGAState *s, int dst, int src, int w, int h)
 {
     int sx = 0, sy = 0;
     int dx = 0, dy = 0;
@@ -724,6 +724,9 @@ static void cirrus_do_copy(CirrusVGAStat
         int width, height;
 
         depth = s->vga.get_bpp(&s->vga) / 8;
+        if (!depth) {
+            return 0;
+        }
         s->vga.get_resolution(&s->vga, &width, &height);
 
         /* extra x, y */
@@ -778,6 +781,8 @@ static void cirrus_do_copy(CirrusVGAStat
     cirrus_invalidate_region(s, s->cirrus_blt_dstaddr,
 				s->cirrus_blt_dstpitch, s->cirrus_blt_width,
 				s->cirrus_blt_height);
+
+    return 1;
 }
 
 static int cirrus_bitblt_videotovideo_copy(CirrusVGAState * s)
@@ -785,11 +790,9 @@ static int cirrus_bitblt_videotovideo_co
     if (blit_is_unsafe(s))
         return 0;
 
-    cirrus_do_copy(s, s->cirrus_blt_dstaddr - s->vga.start_addr,
+    return cirrus_do_copy(s, s->cirrus_blt_dstaddr - s->vga.start_addr,
             s->cirrus_blt_srcaddr - s->vga.start_addr,
             s->cirrus_blt_width, s->cirrus_blt_height);
-
-    return 1;
 }
 
 /***************************************