bugtraq - xorg server 6.8.2 and below on 64bit arch

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Date: 8 Jan 2006 15:26:05 -0000
From: serj@...na.net
To: bugtraq@...urityfocus.com
Subject: xorg server 6.8.2 and below on 64bit arch

This might be nothing or might be something comment please! My system is 64bit turion with 64 bit ubuntu on top. On this machine long = void* = 8 bytes. On a 32 bit arch long = void* = 4 bytes.
Great now lets have look on this.

typedef struct {
 int type;     
 unsigned long serial;   
 Bool send_event; 
 Display *display; 
 Window window;
 Atom message_type;
 int format;
   union {
          char b[20];
          short s[10];
          long l[5];
  } data;
} XClientMessageEvent;

struct taken from the man page (the same lays into Xlib.h) , which later says: "The format member is set to 8, 16, or 32 and specifies whether the data should be viewed as a list of bytes, shorts, or longs."

Problems:
1) if i choose to pass a long through this msg the X server is gonna screw it up. On the other end all i am gonna recieve is 0xffffffff+theotherhalf
I don't know what you think but i think on a 64 bit arch it could be used to crash an app atleast.
2) From the union 5*8 = 40 != 20 therefor XClientMessageEvent is 20 bytes LONGER on a 64 bit arch than on 32 bit. 

Again comment pls as i spot some more code like this in Xlib.h