// gpu_driver_sim.c - Simulated GPU driver ioctl with race condition
#include <stdio.h>
#include <pthread.h>
#include <unistd.h>
#include <string.h>

void *gpu_mmap = NULL;
size_t map_size = 0;
int locked = 0;

void ioctl_map(size_t size) {
    // Allocate GPU memory and map to user
    gpu_mmap = malloc(size);
    map_size = size;
    // Simulate race: after mapping, kernel updates metadata
    usleep(100);  // vulnerable window
    // During this window, another thread can change size causing OOB access
    memset(gpu_mmap, 0, size);
}

void *attacker_thread(void *arg) {
    // While mapping in progress, trigger another ioctl that frees the buffer
    free(gpu_mmap);
    gpu_mmap = NULL;
    return NULL;
}

int main() {
    pthread_t t;
    pthread_create(&t, NULL, attacker_thread, NULL);
    ioctl_map(0x1000);
    pthread_join(t, NULL);
    // Use after free possible
    if (gpu_mmap) memset(gpu_mmap, 'A', 0x1000);  // crash
    return 0;
}

gcc -o gpu_driver_sim gpu_driver_sim.c -lpthread
./gpu_driver_sim