vmsvga: don't process more than 1024 fifo commands at once

vmsvga_fifo_run is called in regular intervals (on each display update)
and will resume where it left off.  So we can simply exit the loop,
without having to worry about how processing will continue.

Fixes: CVE-2016-4453
Cc: qemu-stable@nongnu.org
Cc: P J P <ppandit@redhat.com>
Reported-by: 李强 <liqiang6-s@360.cn>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 1464592161-18348-5-git-send-email-kraxel@redhat.com
(cherry picked from commit 4e68a0ee17dad7b8d870df0081d4ab2e079016c2)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/hw/display/vmware_vga.c b/hw/display/vmware_vga.c
index de2567b0096a60ee0de4cffa5659fd3a3d096938..e51a05ea7e48505af029ae9e5e9b0a243812d1d0 100644 (file)
--- a/hw/display/vmware_vga.c
+++ b/hw/display/vmware_vga.c
@@ -597,13 +597,13 @@ static inline uint32_t vmsvga_fifo_read(struct vmsvga_state_s *s)
 static void vmsvga_fifo_run(struct vmsvga_state_s *s)
 {
     uint32_t cmd, colour;
-    int args, len;
+    int args, len, maxloop = 1024;
     int x, y, dx, dy, width, height;
     struct vmsvga_cursor_definition_s cursor;
     uint32_t cmd_start;
 
     len = vmsvga_fifo_length(s);
-    while (len > 0) {
+    while (len > 0 && --maxloop > 0) {
         /* May need to go back to the start of the command if incomplete */
         cmd_start = s->fifo_stop;