[Qemu-devel] [PATCH] vnc: fix overflow in vnc_update_stats

[Qemu-devel] [PATCH] vnc: fix overflow in vnc_update_stats

[Gerd Hoffmann]

Commit "bea60dd ui/vnc: fix potential memory corruption issues" is
incomplete.  vnc_update_stats must calculate width and height the same
way vnc_refresh_server_surface does it, to make sure we don't use width
and height values larger than the qemu vnc server can handle.

Commit "e22492d ui/vnc: disable adaptive update calculations if not
needed" masks the issue in the default configuration.  It triggers only
in case the "lossy" option is set to "on" (default is "off").

Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 ui/vnc.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/ui/vnc.c b/ui/vnc.c
index 29aa9c4..e7c029d 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -2756,8 +2756,10 @@ static int vnc_refresh_lossy_rect(VncDisplay *vd, int x, int y)
 
 static int vnc_update_stats(VncDisplay *vd,  struct timeval * tv)
 {
-    int width = pixman_image_get_width(vd->guest.fb);
-    int height = pixman_image_get_height(vd->guest.fb);
+    int width = MIN(pixman_image_get_width(vd->guest.fb),
+                    pixman_image_get_width(vd->server));
+    int height = MIN(pixman_image_get_height(vd->guest.fb),
+                     pixman_image_get_height(vd->server));
     int x, y;
     struct timeval res;
     int has_dirty = 0;
-- 
1.8.3.1

Re: [Qemu-devel] [PATCH] vnc: fix overflow in vnc_update_stats

[Marc-André Lureau]

Hi

----- Original Message -----
> Commit "bea60dd ui/vnc: fix potential memory corruption issues" is
> incomplete.  vnc_update_stats must calculate width and height the same
> way vnc_refresh_server_surface does it, to make sure we don't use width
> and height values larger than the qemu vnc server can handle.
> 
> Commit "e22492d ui/vnc: disable adaptive update calculations if not
> needed" masks the issue in the default configuration.  It triggers only
> in case the "lossy" option is set to "on" (default is "off").
> 
> Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

> ---
>  ui/vnc.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/ui/vnc.c b/ui/vnc.c
> index 29aa9c4..e7c029d 100644
> --- a/ui/vnc.c
> +++ b/ui/vnc.c
> @@ -2756,8 +2756,10 @@ static int vnc_refresh_lossy_rect(VncDisplay *vd, int
> x, int y)
>  
>  static int vnc_update_stats(VncDisplay *vd,  struct timeval * tv)
>  {
> -    int width = pixman_image_get_width(vd->guest.fb);
> -    int height = pixman_image_get_height(vd->guest.fb);
> +    int width = MIN(pixman_image_get_width(vd->guest.fb),
> +                    pixman_image_get_width(vd->server));
> +    int height = MIN(pixman_image_get_height(vd->guest.fb),
> +                     pixman_image_get_height(vd->server));
>      int x, y;
>      struct timeval res;
>      int has_dirty = 0;
> --
> 1.8.3.1
> 
>