From: Gerd Hoffmann <kraxel@redhat.com>

Date: Mon, 30 May 2016 09:09:18 +0200

Subject: [PATCH] vmsvga: move fifo sanity checks to vmsvga_fifo_length

MIME-Version: 1.0

Content-Type: text/plain; charset=UTF-8

Content-Transfer-Encoding: 8bit

Sanity checks are applied when the fifo is enabled by the guest

(SVGA_REG_CONFIG_DONE write).  Which doesn't help much if the guest

changes the fifo registers afterwards.  Move the checks to

vmsvga_fifo_length so they are done each time qemu is about to read

from the fifo.

Fixes: CVE-2016-4454

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: 1464592161-18348-2-git-send-email-kraxel@redhat.com

(cherry picked from commit 521360267876d3b6518b328051a2e56bca55bef8)

---

 hw/display/vmware_vga.c | 28 +++++++++++++++-------------

 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/hw/display/vmware_vga.c b/hw/display/vmware_vga.c

index 0c63fa8..63a7c05 100644

--- a/hw/display/vmware_vga.c

+++ b/hw/display/vmware_vga.c

@@ -555,6 +555,21 @@ static inline int vmsvga_fifo_length(struct vmsvga_state_s *s)

     if (!s->config || !s->enable) {

         return 0;

     }

+

+    /* Check range and alignment.  */

+    if ((CMD(min) | CMD(max) | CMD(next_cmd) | CMD(stop)) & 3) {

+        return 0;

+    }

+    if (CMD(min) < (uint8_t *) s->cmd->fifo - (uint8_t *) s->fifo) {

+        return 0;

+    }

+    if (CMD(max) > SVGA_FIFO_SIZE) {

+        return 0;

+    }

+    if (CMD(max) < CMD(min) + 10 * 1024) {

+        return 0;

+    }

+

     num = CMD(next_cmd) - CMD(stop);

     if (num < 0) {

         num += CMD(max) - CMD(min);

@@ -1005,19 +1020,6 @@ static void vmsvga_value_write(void *opaque, uint32_t address, uint32_t value)

     case SVGA_REG_CONFIG_DONE:

         if (value) {

             s->fifo = (uint32_t *) s->fifo_ptr;

-            /* Check range and alignment.  */

-            if ((CMD(min) | CMD(max) | CMD(next_cmd) | CMD(stop)) & 3) {

-                break;

-            }

-            if (CMD(min) < (uint8_t *) s->cmd->fifo - (uint8_t *) s->fifo) {

-                break;

-            }

-            if (CMD(max) > SVGA_FIFO_SIZE) {

-                break;

-            }

-            if (CMD(max) < CMD(min) + 10 * 1024) {

-                break;

-            }

             vga_dirty_log_stop(&s->vga);

         }

         s->config = !!value;