[Qemu-devel] [PATCH 1/1] vmware_vga: stop crashing

[Serge Hallyn <serge.hallyn@canonical.com>]

if x or y < 0, set them to 0 (and decrement width/height accordingly)>

I don't know where the best place to catch this would be, but
with vnc and vmware_vga it's possible to get set_bit called on
a negative index, crashing qemu.  See

https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/918791

for details.  This patch prevents that.  It's possible this
should be caught earlier, but this patch works for me.

Changelog:
	Mar 5: As Ryan Harper pointed out, don't mix tabs+spaces,
	       and put {} around all conditionals.

Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com>
---
 hw/vmware_vga.c |   18 ++++++++++++++++++
 1 files changed, 18 insertions(+), 0 deletions(-)

diff --git a/hw/vmware_vga.c b/hw/vmware_vga.c
index 142d9f4..c94f9f3 100644
--- a/hw/vmware_vga.c
+++ b/hw/vmware_vga.c
@@ -298,6 +298,24 @@ static inline void vmsvga_update_rect(struct vmsvga_state_s *s,
     uint8_t *src;
     uint8_t *dst;
 
+    if (x < 0) {
+        fprintf(stderr, "%s: update x was < 0 (%d, w %d)\n",
+                        __FUNCTION__, x, w);
+        w += x;
+        if (w < 0) {
+            return;
+        }
+        x = 0;
+    }
+    if (y < 0) {
+        fprintf(stderr, "%s: update y was < 0 (%d, h %d)\n",
+                        __FUNCTION__, y, h);
+        h += y;
+        if (h < 0) {
+            return;
+        }
+        y = 0;
+    }
     if (x + w > s->width) {
         fprintf(stderr, "%s: update width too large x: %d, w: %d\n",
                         __FUNCTION__, x, w);
-- 
1.7.9