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Bug#640080: marked as done (xvfb: Xvfb segfaults when a bit depth other than 8, 15, 16, 24, or 30 requested)

Your message dated Wed, 18 Jul 2012 11:28:05 +0200
with message-id <20120718092805.GU7369@radis.cristau.org>
and subject line Re: Bug#640080: xvfb: Xvfb segfaults when a bit depth other than 8, 15, 16, 24, or 30 requested
has caused the Debian Bug report #640080,
regarding xvfb: Xvfb segfaults when a bit depth other than 8, 15, 16, 24, or 30 requested
to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.

(NB: If you are a system administrator and have no idea what this
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immediately.)


-- 
640080: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=640080
Debian Bug Tracking System
Contact owner@bugs.debian.org with problems
--- Begin Message --- 
Package: xvfb
Version: 2:1.11.0-1
Severity: normal

If Xvfb is started with a bit depth of anything other than 8, 15, 16,
24, or 30, it segfaults.

This appears to be due to a missing case in
InitOutput.c:vfbScreenInit. At line 832 there's a "switch
(pvfb->depth)" and thus explicit support for only the aforementioned
display depths. When a bit depth other than the above is requested,
the micmap.c:miVisuals array is never filled with useful values and a
null pointer is dereferenced (micmap.c:miInitVisuals at the end where
it says depth[i].vids[j]). 

I'd prefer some attempt to pick sane defaults when the user requests a
nonconventional bitdepth, but erroring out is definitely better than a
segfault. 

Obviously this is not very important -- after all, no one seems to
have mentioned it before -- and the only mode I was actively thinking
about wanting was the 1bpp mode for testing. But since Xvfb is
mentioned as also being used for "testing clients against unusual
depths", it would be nice to actually support said unusual depths. 

Thank you!

 - Robert Jacobs

p.s. Adding support for 1bpp seems to just involves adding:
    case 1:
        miSetVisualTypesAndMasks (1,
                                  (1 << StaticGray),
                                  1, StaticGray, 0, 0, 0);
        break;

I also have tested the following code for some sort of default for all
other depths, but it's rather ugly:
   default:
	    if (pvfb->depth > 8) {
		    int bluemask = (1 << (pvfb->depth/3)) - 1;
		    int greenmask = ((1 << ((2+pvfb->depth)/3)) - 1) 
			    << (pvfb->depth/3);
		    int redmask = ((1 << pvfb->depth)-1) & (~bluemask) & (~greenmask);
		    miSetVisualTypesAndMasks 
			    (pvfb->depth,
			     ((1 << TrueColor) |
			      (1 << DirectColor)),
			     (2+pvfb->depth)/3>8?(2+pvfb->depth)/3:8, 
			     TrueColor, redmask, greenmask, bluemask);
	    } else if (pvfb->depth < 8) {
        miSetVisualTypesAndMasks (pvfb->depth,
                                  ((1 << StaticGray) |
                                   (1 << GrayScale) |
                                   (1 << StaticColor) |
                                   (1 << PseudoColor) |
                                   (1 << TrueColor) |
                                   (1 << DirectColor)),
                                  8, PseudoColor, 0, 0, 0);
	    }
	    break;


-- System Information:
Debian Release: wheezy/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (500, 'stable')
Architecture: i386 (i686)

Kernel: Linux 3.0.0-1-686-pae (SMP w/1 CPU core)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages xvfb depends on:
ii  libaudit0       1.7.18-1  
ii  libc6           2.13-18   
ii  libgcrypt11     1.4.6-9   
ii  libpixman-1-0   0.22.2-1  
ii  libselinux1     2.1.0-1   
ii  libxau6         1:1.0.6-3 
ii  libxdmcp6       1:1.1.0-3 
ii  libxfont1       1:1.4.4-1 
ii  xserver-common  2:1.11.0-1

Versions of packages xvfb recommends:
ii  xauth  1:1.0.6-1

xvfb suggests no packages.

-- no debconf information

--- End Message ---
--- Begin Message --- 
Version: 2:1.11.99.1-1

On Thu, Jan  5, 2012 at 01:49:38 -0800, Robert Jacobs wrote:

> 
> This is fd.o bug 38420, they seem to have cleanly disabled nonstandard bitdepths:
>  https://bugs.freedesktop.org/show_bug.cgi?id=38420
> 
Right.  Marking as fixed, thanks for the report.

Cheers,
Julien

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