[Qemu-devel] [PATCH] ui: vnc: avoid floating point exception

[P J P]

  Hello Gerd,

A floating point exception issue in the VNC server PNG compression support was 
reported by Mr Lian Yihan, CC'd here. Given below is a proposed (tested)patch 
to fix this issue.

===
> From 1ca4818333d39fed6567e316e37f6a6516f59c69 Mon Sep 17 00:00:00 2001
From: Prasad J Pandit <address@hidden>
Date: Thu, 3 Dec 2015 16:04:51 +0530
Subject: [PATCH] ui: vnc: avoid floating point exception

While sending 'SetPixelFormat' messages to a VNC server,
the client could set the 'red-max', 'green-max' and 'blue-max'
values to be zero. This leads to a floating point exception in
write_png_palette while doing frame buffer updates.

Reported-by: Lian Yihan <address@hidden>
Signed-off-by: Prasad J Pandit <address@hidden>
---
 ui/vnc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/ui/vnc.c b/ui/vnc.c
index caf82f5..52c6809 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -2189,15 +2189,15 @@ static void set_pixel_format(VncState *vs,
         return;
     }

-    vs->client_pf.rmax = red_max;
+    vs->client_pf.rmax = red_max ? red_max : 0xFF;
     vs->client_pf.rbits = hweight_long(red_max);
     vs->client_pf.rshift = red_shift;
     vs->client_pf.rmask = red_max << red_shift;
-    vs->client_pf.gmax = green_max;
+    vs->client_pf.gmax = green_max ? green_max : 0xFF;
     vs->client_pf.gbits = hweight_long(green_max);
     vs->client_pf.gshift = green_shift;
     vs->client_pf.gmask = green_max << green_shift;
-    vs->client_pf.bmax = blue_max;
+    vs->client_pf.bmax = blue_max ? blue_max : 0xFF;
     vs->client_pf.bbits = hweight_long(blue_max);
     vs->client_pf.bshift = blue_shift;
     vs->client_pf.bmask = blue_max << blue_shift;
--
2.4.3
===


Thank you.
--
Prasad J Pandit / Red Hat Product Security Team
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