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Subjectperf_event_open+clone = unkillable process
Hello,

The following program creates an unkillable process that eats CPU.
/proc/pid/stack is empty, I am not sure what other info I can provide.

Tested is on upstream commit 4aa9fc2a435abe95a1e8d7f8c7b3d6356514b37a.
Config is attached.

FTR, generated from the following syzkaller program:

perf_event_open(&(0x7f0000000580)={0x2, 0x70, 0x5c61, 0x2, 0x0, 0x0,
0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, @perf_config_ext}, 0x0,
0xffffffffffffffff, 0xffffffffffffffff, 0x0)
clone(0x20002100, 0x0, 0xfffffffffffffffe, 0x0, 0xffffffffffffffff)
r0 = gettid()
timer_create(0x0, &(0x7f0000000000)={0x0, 0x7, 0x4, @tid=r0}, &(0x7f0000000080))
timer_settime(0x0, 0x3, &(0x7f0000000140)={{0x0, 0x1}, {0x0, 0x1c9c380}}, 0x0)


// autogenerated by syzkaller (https://github.com/google/syzkaller)
#define _GNU_SOURCE
#include <endian.h>
#include <errno.h>
#include <pthread.h>
#include <setjmp.h>
#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>

#include <linux/futex.h>

static __thread int skip_segv;
static __thread jmp_buf segv_env;

static void segv_handler(int sig, siginfo_t* info, void* ctx)
{
uintptr_t addr = (uintptr_t)info->si_addr;
const uintptr_t prog_start = 1 << 20;
const uintptr_t prog_end = 100 << 20;
if (__atomic_load_n(&skip_segv, __ATOMIC_RELAXED) &&
(addr < prog_start || addr > prog_end)) {
_longjmp(segv_env, 1);
}
exit(sig);
}

static void install_segv_handler(void)
{
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_handler = SIG_IGN;
syscall(SYS_rt_sigaction, 0x20, &sa, NULL, 8);
syscall(SYS_rt_sigaction, 0x21, &sa, NULL, 8);
memset(&sa, 0, sizeof(sa));
sa.sa_sigaction = segv_handler;
sa.sa_flags = SA_NODEFER | SA_SIGINFO;
sigaction(SIGSEGV, &sa, NULL);
sigaction(SIGBUS, &sa, NULL);
}

#define NONFAILING(...) \
{ \
__atomic_fetch_add(&skip_segv, 1, __ATOMIC_SEQ_CST); \
if (_setjmp(segv_env) == 0) { \
__VA_ARGS__; \
} \
__atomic_fetch_sub(&skip_segv, 1, __ATOMIC_SEQ_CST); \
}

static void sleep_ms(uint64_t ms)
{
usleep(ms * 1000);
}

static uint64_t current_time_ms(void)
{
struct timespec ts;
if (clock_gettime(CLOCK_MONOTONIC, &ts))
exit(1);
return (uint64_t)ts.tv_sec * 1000 + (uint64_t)ts.tv_nsec / 1000000;
}

static void thread_start(void* (*fn)(void*), void* arg)
{
pthread_t th;
pthread_attr_t attr;
pthread_attr_init(&attr);
pthread_attr_setstacksize(&attr, 128 << 10);
int i;
for (i = 0; i < 100; i++) {
if (pthread_create(&th, &attr, fn, arg) == 0) {
pthread_attr_destroy(&attr);
return;
}
if (errno == EAGAIN) {
usleep(50);
continue;
}
break;
}
exit(1);
}

#define BITMASK(bf_off, bf_len) (((1ull << (bf_len)) - 1) << (bf_off))
#define STORE_BY_BITMASK(type, htobe, addr, val, bf_off, bf_len) \
*(type*)(addr) = \
htobe((htobe(*(type*)(addr)) & ~BITMASK((bf_off), (bf_len))) | \
(((type)(val) << (bf_off)) & BITMASK((bf_off), (bf_len))))

typedef struct {
int state;
} event_t;

static void event_init(event_t* ev)
{
ev->state = 0;
}

static void event_reset(event_t* ev)
{
ev->state = 0;
}

static void event_set(event_t* ev)
{
if (ev->state)
exit(1);
__atomic_store_n(&ev->state, 1, __ATOMIC_RELEASE);
syscall(SYS_futex, &ev->state, FUTEX_WAKE | FUTEX_PRIVATE_FLAG);
}

static void event_wait(event_t* ev)
{
while (!__atomic_load_n(&ev->state, __ATOMIC_ACQUIRE))
syscall(SYS_futex, &ev->state, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, 0, 0);
}

static int event_isset(event_t* ev)
{
return __atomic_load_n(&ev->state, __ATOMIC_ACQUIRE);
}

static int event_timedwait(event_t* ev, uint64_t timeout)
{
uint64_t start = current_time_ms();
uint64_t now = start;
for (;;) {
uint64_t remain = timeout - (now - start);
struct timespec ts;
ts.tv_sec = remain / 1000;
ts.tv_nsec = (remain % 1000) * 1000 * 1000;
syscall(SYS_futex, &ev->state, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, 0, &ts);
if (__atomic_load_n(&ev->state, __ATOMIC_RELAXED))
return 1;
now = current_time_ms();
if (now - start > timeout)
return 0;
}
}

struct thread_t {
int created, call;
event_t ready, done;
};

static struct thread_t threads[16];
static void execute_call(int call);
static int running;

static void* thr(void* arg)
{
struct thread_t* th = (struct thread_t*)arg;
for (;;) {
event_wait(&th->ready);
event_reset(&th->ready);
execute_call(th->call);
__atomic_fetch_sub(&running, 1, __ATOMIC_RELAXED);
event_set(&th->done);
}
return 0;
}

static void loop(void)
{
int i, call, thread;
for (call = 0; call < 5; call++) {
for (thread = 0; thread < (int)(sizeof(threads) / sizeof(threads[0]));
thread++) {
struct thread_t* th = &threads[thread];
if (!th->created) {
th->created = 1;
event_init(&th->ready);
event_init(&th->done);
event_set(&th->done);
thread_start(thr, th);
}
if (!event_isset(&th->done))
continue;
event_reset(&th->done);
th->call = call;
__atomic_fetch_add(&running, 1, __ATOMIC_RELAXED);
event_set(&th->ready);
event_timedwait(&th->done, 45);
break;
}
}
for (i = 0; i < 100 && __atomic_load_n(&running, __ATOMIC_RELAXED); i++)
sleep_ms(1);
}

uint64_t r[1] = {0x0};

void execute_call(int call)
{
long res;
switch (call) {
case 0:
NONFAILING(*(uint32_t*)0x20000580 = 2);
NONFAILING(*(uint32_t*)0x20000584 = 0x70);
NONFAILING(*(uint8_t*)0x20000588 = 0x61);
NONFAILING(*(uint8_t*)0x20000589 = 2);
NONFAILING(*(uint8_t*)0x2000058a = 0);
NONFAILING(*(uint8_t*)0x2000058b = 0);
NONFAILING(*(uint32_t*)0x2000058c = 0);
NONFAILING(*(uint64_t*)0x20000590 = 0);
NONFAILING(*(uint64_t*)0x20000598 = 0);
NONFAILING(*(uint64_t*)0x200005a0 = 0);
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 0, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 1, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 2, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 3, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 4, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 5, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 6, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 7, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 8, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 9, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 10, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 11, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 12, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 13, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 14, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 15, 2));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 17, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 18, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 19, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 20, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 21, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 22, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 23, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 24, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 25, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 26, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 27, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 28, 1));
NONFAILING(STORE_BY_BITMASK(uint64_t, , 0x200005a8, 0, 29, 35));
NONFAILING(*(uint32_t*)0x200005b0 = 0);
NONFAILING(*(uint32_t*)0x200005b4 = 0);
NONFAILING(*(uint64_t*)0x200005b8 = 0);
NONFAILING(*(uint64_t*)0x200005c0 = 0);
NONFAILING(*(uint64_t*)0x200005c8 = 0);
NONFAILING(*(uint64_t*)0x200005d0 = 0);
NONFAILING(*(uint32_t*)0x200005d8 = 0);
NONFAILING(*(uint32_t*)0x200005dc = 0);
NONFAILING(*(uint64_t*)0x200005e0 = 0);
NONFAILING(*(uint32_t*)0x200005e8 = 0);
NONFAILING(*(uint16_t*)0x200005ec = 0);
NONFAILING(*(uint16_t*)0x200005ee = 0);
syscall(__NR_perf_event_open, 0x20000580, 0, -1, -1, 0);
break;
case 1:
syscall(__NR_clone, 0x20002100, 0, 0x9999999999999999, 0, -1);
break;
case 2:
res = syscall(__NR_gettid);
if (res != -1)
r[0] = res;
break;
case 3:
NONFAILING(*(uint64_t*)0x20000000 = 0);
NONFAILING(*(uint32_t*)0x20000008 = 7);
NONFAILING(*(uint32_t*)0x2000000c = 4);
NONFAILING(*(uint32_t*)0x20000010 = r[0]);
syscall(__NR_timer_create, 0, 0x20000000, 0x20000080);
break;
case 4:
NONFAILING(*(uint64_t*)0x20000140 = 0);
NONFAILING(*(uint64_t*)0x20000148 = 1);
NONFAILING(*(uint64_t*)0x20000150 = 0);
NONFAILING(*(uint64_t*)0x20000158 = 0x1c9c380);
syscall(__NR_timer_settime, 0, 3, 0x20000140, 0);
break;
}
}
int main(void)
{
syscall(__NR_mmap, 0x20000000, 0x1000000, 3, 0x32, -1, 0);
install_segv_handler();
loop();
return 0;
}
[unhandled content-type:application/octet-stream]
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