debian/patches/extra/0004-vmsvga-move-fifo-sanity-checks-to-vmsvga_fifo_length.patch

   1 From 4aa79a8818711d475bd79b906cd7d060d4e8a441 Mon Sep 17 00:00:00 2001
   2 From: Gerd Hoffmann <kraxel@redhat.com>
   3 Date: Mon, 30 May 2016 09:09:18 +0200
   4 Subject: [PATCH 4/9] vmsvga: move fifo sanity checks to vmsvga_fifo_length
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   8
   9 Sanity checks are applied when the fifo is enabled by the guest
  10 (SVGA_REG_CONFIG_DONE write).  Which doesn't help much if the guest
  11 changes the fifo registers afterwards.  Move the checks to
  12 vmsvga_fifo_length so they are done each time qemu is about to read
  13 from the fifo.
  14
  15 Fixes: CVE-2016-4454
  16 Cc: P J P <ppandit@redhat.com>
  17 Reported-by: 李强 <liqiang6-s@360.cn>
  18 Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
  19 ---
  20  hw/display/vmware_vga.c | 28 +++++++++++++++-------------
  21  1 file changed, 15 insertions(+), 13 deletions(-)
  22
  23 diff --git a/hw/display/vmware_vga.c b/hw/display/vmware_vga.c
  24 index 9354037..3ce1717 100644
  25 --- a/hw/display/vmware_vga.c
  26 +++ b/hw/display/vmware_vga.c
  27 @@ -553,6 +553,21 @@ static inline int vmsvga_fifo_length(struct vmsvga_state_s *s)
  28      if (!s->config || !s->enable) {
  29          return 0;
  30      }
  31 +
  32 +    /* Check range and alignment.  */
  33 +    if ((CMD(min) | CMD(max) | CMD(next_cmd) | CMD(stop)) & 3) {
  34 +        return 0;
  35 +    }
  36 +    if (CMD(min) < (uint8_t *) s->cmd->fifo - (uint8_t *) s->fifo) {
  37 +        return 0;
  38 +    }
  39 +    if (CMD(max) > SVGA_FIFO_SIZE) {
  40 +        return 0;
  41 +    }
  42 +    if (CMD(max) < CMD(min) + 10 * 1024) {
  43 +        return 0;
  44 +    }
  45 +
  46      num = CMD(next_cmd) - CMD(stop);
  47      if (num < 0) {
  48          num += CMD(max) - CMD(min);
  49 @@ -1003,19 +1018,6 @@ static void vmsvga_value_write(void *opaque, uint32_t address, uint32_t value)
  50      case SVGA_REG_CONFIG_DONE:
  51          if (value) {
  52              s->fifo = (uint32_t *) s->fifo_ptr;
  53 -            /* Check range and alignment.  */
  54 -            if ((CMD(min) | CMD(max) | CMD(next_cmd) | CMD(stop)) & 3) {
  55 -                break;
  56 -            }
  57 -            if (CMD(min) < (uint8_t *) s->cmd->fifo - (uint8_t *) s->fifo) {
  58 -                break;
  59 -            }
  60 -            if (CMD(max) > SVGA_FIFO_SIZE) {
  61 -                break;
  62 -            }
  63 -            if (CMD(max) < CMD(min) + 10 * 1024) {
  64 -                break;
  65 -            }
  66              vga_dirty_log_stop(&s->vga);
  67          }
  68          s->config = !!value;
  69 --
  70 2.1.4
  71