syzkaller-repros/linux/226979e84dbedfe6af2c9b750bcdd24ff209279b.c

// KASAN: slab-out-of-bounds Read in linear_transfer
// https://syzkaller.appspot.com/bug?id=226979e84dbedfe6af2c9b750bcdd24ff209279b
// status:fixed
// autogenerated by syzkaller (https://github.com/google/syzkaller)

#define _GNU_SOURCE

#include <arpa/inet.h>
#include <dirent.h>
#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <net/if.h>
#include <netinet/in.h>
#include <pthread.h>
#include <signal.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/prctl.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>

#include <linux/futex.h>
#include <linux/genetlink.h>
#include <linux/if_addr.h>
#include <linux/if_link.h>
#include <linux/in6.h>
#include <linux/neighbour.h>
#include <linux/net.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <linux/veth.h>

unsigned long long procid;

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;
  }
}

static bool write_file(const char* file, const char* what, ...)
{
  char buf[1024];
  va_list args;
  va_start(args, what);
  vsnprintf(buf, sizeof(buf), what, args);
  va_end(args);
  buf[sizeof(buf) - 1] = 0;
  int len = strlen(buf);
  int fd = open(file, O_WRONLY | O_CLOEXEC);
  if (fd == -1)
    return false;
  if (write(fd, buf, len) != len) {
    int err = errno;
    close(fd);
    errno = err;
    return false;
  }
  close(fd);
  return true;
}

struct nlmsg {
  char* pos;
  int nesting;
  struct nlattr* nested[8];
  char buf[1024];
};

static struct nlmsg nlmsg;

static void netlink_init(struct nlmsg* nlmsg, int typ, int flags,
                         const void* data, int size)
{
  memset(nlmsg, 0, sizeof(*nlmsg));
  struct nlmsghdr* hdr = (struct nlmsghdr*)nlmsg->buf;
  hdr->nlmsg_type = typ;
  hdr->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK | flags;
  memcpy(hdr + 1, data, size);
  nlmsg->pos = (char*)(hdr + 1) + NLMSG_ALIGN(size);
}

static void netlink_attr(struct nlmsg* nlmsg, int typ, const void* data,
                         int size)
{
  struct nlattr* attr = (struct nlattr*)nlmsg->pos;
  attr->nla_len = sizeof(*attr) + size;
  attr->nla_type = typ;
  memcpy(attr + 1, data, size);
  nlmsg->pos += NLMSG_ALIGN(attr->nla_len);
}

static int netlink_send_ext(struct nlmsg* nlmsg, int sock, uint16_t reply_type,
                            int* reply_len)
{
  if (nlmsg->pos > nlmsg->buf + sizeof(nlmsg->buf) || nlmsg->nesting)
    exit(1);
  struct nlmsghdr* hdr = (struct nlmsghdr*)nlmsg->buf;
  hdr->nlmsg_len = nlmsg->pos - nlmsg->buf;
  struct sockaddr_nl addr;
  memset(&addr, 0, sizeof(addr));
  addr.nl_family = AF_NETLINK;
  unsigned n = sendto(sock, nlmsg->buf, hdr->nlmsg_len, 0,
                      (struct sockaddr*)&addr, sizeof(addr));
  if (n != hdr->nlmsg_len)
    exit(1);
  n = recv(sock, nlmsg->buf, sizeof(nlmsg->buf), 0);
  if (hdr->nlmsg_type == NLMSG_DONE) {
    *reply_len = 0;
    return 0;
  }
  if (n < sizeof(struct nlmsghdr))
    exit(1);
  if (reply_len && hdr->nlmsg_type == reply_type) {
    *reply_len = n;
    return 0;
  }
  if (n < sizeof(struct nlmsghdr) + sizeof(struct nlmsgerr))
    exit(1);
  if (hdr->nlmsg_type != NLMSG_ERROR)
    exit(1);
  return -((struct nlmsgerr*)(hdr + 1))->error;
}

static int netlink_send(struct nlmsg* nlmsg, int sock)
{
  return netlink_send_ext(nlmsg, sock, 0, NULL);
}

static int netlink_next_msg(struct nlmsg* nlmsg, unsigned int offset,
                            unsigned int total_len)
{
  struct nlmsghdr* hdr = (struct nlmsghdr*)(nlmsg->buf + offset);
  if (offset == total_len || offset + hdr->nlmsg_len > total_len)
    return -1;
  return hdr->nlmsg_len;
}

static void netlink_device_change(struct nlmsg* nlmsg, int sock,
                                  const char* name, bool up, const char* master,
                                  const void* mac, int macsize,
                                  const char* new_name)
{
  struct ifinfomsg hdr;
  memset(&hdr, 0, sizeof(hdr));
  if (up)
    hdr.ifi_flags = hdr.ifi_change = IFF_UP;
  hdr.ifi_index = if_nametoindex(name);
  netlink_init(nlmsg, RTM_NEWLINK, 0, &hdr, sizeof(hdr));
  if (new_name)
    netlink_attr(nlmsg, IFLA_IFNAME, new_name, strlen(new_name));
  if (master) {
    int ifindex = if_nametoindex(master);
    netlink_attr(nlmsg, IFLA_MASTER, &ifindex, sizeof(ifindex));
  }
  if (macsize)
    netlink_attr(nlmsg, IFLA_ADDRESS, mac, macsize);
  int err = netlink_send(nlmsg, sock);
  (void)err;
}

const int kInitNetNsFd = 239;

#define DEVLINK_FAMILY_NAME "devlink"

#define DEVLINK_CMD_PORT_GET 5
#define DEVLINK_CMD_RELOAD 37
#define DEVLINK_ATTR_BUS_NAME 1
#define DEVLINK_ATTR_DEV_NAME 2
#define DEVLINK_ATTR_NETDEV_NAME 7
#define DEVLINK_ATTR_NETNS_FD 138

static int netlink_devlink_id_get(struct nlmsg* nlmsg, int sock)
{
  struct genlmsghdr genlhdr;
  struct nlattr* attr;
  int err, n;
  uint16_t id = 0;
  memset(&genlhdr, 0, sizeof(genlhdr));
  genlhdr.cmd = CTRL_CMD_GETFAMILY;
  netlink_init(nlmsg, GENL_ID_CTRL, 0, &genlhdr, sizeof(genlhdr));
  netlink_attr(nlmsg, CTRL_ATTR_FAMILY_NAME, DEVLINK_FAMILY_NAME,
               strlen(DEVLINK_FAMILY_NAME) + 1);
  err = netlink_send_ext(nlmsg, sock, GENL_ID_CTRL, &n);
  if (err) {
    return -1;
  }
  attr = (struct nlattr*)(nlmsg->buf + NLMSG_HDRLEN +
                          NLMSG_ALIGN(sizeof(genlhdr)));
  for (; (char*)attr < nlmsg->buf + n;
       attr = (struct nlattr*)((char*)attr + NLMSG_ALIGN(attr->nla_len))) {
    if (attr->nla_type == CTRL_ATTR_FAMILY_ID) {
      id = *(uint16_t*)(attr + 1);
      break;
    }
  }
  if (!id) {
    return -1;
  }
  recv(sock, nlmsg->buf, sizeof(nlmsg->buf), 0); /* recv ack */
  return id;
}

static void netlink_devlink_netns_move(const char* bus_name,
                                       const char* dev_name, int netns_fd)
{
  struct genlmsghdr genlhdr;
  int sock;
  int id, err;
  sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_GENERIC);
  if (sock == -1)
    exit(1);
  id = netlink_devlink_id_get(&nlmsg, sock);
  if (id == -1)
    goto error;
  memset(&genlhdr, 0, sizeof(genlhdr));
  genlhdr.cmd = DEVLINK_CMD_RELOAD;
  netlink_init(&nlmsg, id, 0, &genlhdr, sizeof(genlhdr));
  netlink_attr(&nlmsg, DEVLINK_ATTR_BUS_NAME, bus_name, strlen(bus_name) + 1);
  netlink_attr(&nlmsg, DEVLINK_ATTR_DEV_NAME, dev_name, strlen(dev_name) + 1);
  netlink_attr(&nlmsg, DEVLINK_ATTR_NETNS_FD, &netns_fd, sizeof(netns_fd));
  err = netlink_send(&nlmsg, sock);
  if (err) {
  }
error:
  close(sock);
}

static struct nlmsg nlmsg2;

static void initialize_devlink_ports(const char* bus_name, const char* dev_name,
                                     const char* netdev_prefix)
{
  struct genlmsghdr genlhdr;
  int len, total_len, id, err, offset;
  uint16_t netdev_index;
  int sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_GENERIC);
  if (sock == -1)
    exit(1);
  int rtsock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
  if (rtsock == -1)
    exit(1);
  id = netlink_devlink_id_get(&nlmsg, sock);
  if (id == -1)
    goto error;
  memset(&genlhdr, 0, sizeof(genlhdr));
  genlhdr.cmd = DEVLINK_CMD_PORT_GET;
  netlink_init(&nlmsg, id, NLM_F_DUMP, &genlhdr, sizeof(genlhdr));
  netlink_attr(&nlmsg, DEVLINK_ATTR_BUS_NAME, bus_name, strlen(bus_name) + 1);
  netlink_attr(&nlmsg, DEVLINK_ATTR_DEV_NAME, dev_name, strlen(dev_name) + 1);
  err = netlink_send_ext(&nlmsg, sock, id, &total_len);
  if (err) {
    goto error;
  }
  offset = 0;
  netdev_index = 0;
  while ((len = netlink_next_msg(&nlmsg, offset, total_len)) != -1) {
    struct nlattr* attr = (struct nlattr*)(nlmsg.buf + offset + NLMSG_HDRLEN +
                                           NLMSG_ALIGN(sizeof(genlhdr)));
    for (; (char*)attr < nlmsg.buf + offset + len;
         attr = (struct nlattr*)((char*)attr + NLMSG_ALIGN(attr->nla_len))) {
      if (attr->nla_type == DEVLINK_ATTR_NETDEV_NAME) {
        char* port_name;
        char netdev_name[IFNAMSIZ];
        port_name = (char*)(attr + 1);
        snprintf(netdev_name, sizeof(netdev_name), "%s%d", netdev_prefix,
                 netdev_index);
        netlink_device_change(&nlmsg2, rtsock, port_name, true, 0, 0, 0,
                              netdev_name);
        break;
      }
    }
    offset += len;
    netdev_index++;
  }
error:
  close(rtsock);
  close(sock);
}

static void initialize_devlink_pci(void)
{
  int netns = open("/proc/self/ns/net", O_RDONLY);
  if (netns == -1)
    exit(1);
  int ret = setns(kInitNetNsFd, 0);
  if (ret == -1)
    exit(1);
  netlink_devlink_netns_move("pci", "0000:00:10.0", netns);
  ret = setns(netns, 0);
  if (ret == -1)
    exit(1);
  close(netns);
  initialize_devlink_ports("pci", "0000:00:10.0", "netpci");
}

static long syz_open_dev(volatile long a0, volatile long a1, volatile long a2)
{
  if (a0 == 0xc || a0 == 0xb) {
    char buf[128];
    sprintf(buf, "/dev/%s/%d:%d", a0 == 0xc ? "char" : "block", (uint8_t)a1,
            (uint8_t)a2);
    return open(buf, O_RDWR, 0);
  } else {
    char buf[1024];
    char* hash;
    strncpy(buf, (char*)a0, sizeof(buf) - 1);
    buf[sizeof(buf) - 1] = 0;
    while ((hash = strchr(buf, '#'))) {
      *hash = '0' + (char)(a1 % 10);
      a1 /= 10;
    }
    return open(buf, a2, 0);
  }
}

static void kill_and_wait(int pid, int* status)
{
  kill(-pid, SIGKILL);
  kill(pid, SIGKILL);
  int i;
  for (i = 0; i < 100; i++) {
    if (waitpid(-1, status, WNOHANG | __WALL) == pid)
      return;
    usleep(1000);
  }
  DIR* dir = opendir("/sys/fs/fuse/connections");
  if (dir) {
    for (;;) {
      struct dirent* ent = readdir(dir);
      if (!ent)
        break;
      if (strcmp(ent->d_name, ".") == 0 || strcmp(ent->d_name, "..") == 0)
        continue;
      char abort[300];
      snprintf(abort, sizeof(abort), "/sys/fs/fuse/connections/%s/abort",
               ent->d_name);
      int fd = open(abort, O_WRONLY);
      if (fd == -1) {
        continue;
      }
      if (write(fd, abort, 1) < 0) {
      }
      close(fd);
    }
    closedir(dir);
  } else {
  }
  while (waitpid(-1, status, __WALL) != pid) {
  }
}

static void setup_test()
{
  prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
  setpgrp();
  write_file("/proc/self/oom_score_adj", "1000");
}

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 execute_one(void)
{
  int i, call, thread;
  int collide = 0;
again:
  for (call = 0; call < 10; 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);
      if (collide && (call % 2) == 0)
        break;
      event_timedwait(&th->done, 45);
      break;
    }
  }
  for (i = 0; i < 100 && __atomic_load_n(&running, __ATOMIC_RELAXED); i++)
    sleep_ms(1);
  if (!collide) {
    collide = 1;
    goto again;
  }
}

static void execute_one(void);

#define WAIT_FLAGS __WALL

static void loop(void)
{
  int iter;
  for (iter = 0;; iter++) {
    int pid = fork();
    if (pid < 0)
      exit(1);
    if (pid == 0) {
      setup_test();
      execute_one();
      exit(0);
    }
    int status = 0;
    uint64_t start = current_time_ms();
    for (;;) {
      if (waitpid(-1, &status, WNOHANG | WAIT_FLAGS) == pid)
        break;
      sleep_ms(1);
      if (current_time_ms() - start < 5 * 1000)
        continue;
      kill_and_wait(pid, &status);
      break;
    }
  }
}

uint64_t r[1] = {0xffffffffffffffff};

void execute_call(int call)
{
  intptr_t res;
  switch (call) {
  case 0:
    *(uint32_t*)0x2001d000 = 1;
    *(uint32_t*)0x2001d004 = 0x70;
    *(uint8_t*)0x2001d008 = 0;
    *(uint8_t*)0x2001d009 = 0;
    *(uint8_t*)0x2001d00a = 0;
    *(uint8_t*)0x2001d00b = 0;
    *(uint32_t*)0x2001d00c = 0;
    *(uint64_t*)0x2001d010 = 0x7f;
    *(uint64_t*)0x2001d018 = 0x8021;
    *(uint64_t*)0x2001d020 = 0;
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 0, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 1, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 2, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 3, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 4, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0x7f, 5, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 6, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 7, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 8, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 9, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 10, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 11, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 12, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 13, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 14, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 15, 2);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 17, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 18, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 19, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 20, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 21, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 22, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 23, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 24, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 25, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 26, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 27, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 28, 1);
    STORE_BY_BITMASK(uint64_t, , 0x2001d028, 0, 29, 35);
    *(uint32_t*)0x2001d030 = 0;
    *(uint32_t*)0x2001d034 = 0;
    *(uint64_t*)0x2001d038 = 0;
    *(uint64_t*)0x2001d040 = 0;
    *(uint64_t*)0x2001d048 = 0;
    *(uint64_t*)0x2001d050 = 0;
    *(uint32_t*)0x2001d058 = 0;
    *(uint32_t*)0x2001d05c = 0;
    *(uint64_t*)0x2001d060 = 0;
    *(uint32_t*)0x2001d068 = 0;
    *(uint16_t*)0x2001d06c = 0;
    *(uint16_t*)0x2001d06e = 0;
    syscall(__NR_perf_event_open, 0x2001d000ul, 0, -1ul, -1, 0ul);
    break;
  case 1:
    memcpy((void*)0x20000000, "/dev/dsp\000", 9);
    res = syscall(__NR_openat, 0xffffffffffffff9cul, 0x20000000ul, 0ul, 0ul);
    if (res != -1)
      r[0] = res;
    break;
  case 2:
    *(uint64_t*)0x20000240 = 0;
    syscall(__NR_ioctl, r[0], 0x800000c004500aul, 0x20000240ul);
    break;
  case 3:
    *(uint64_t*)0x200000c0 = 0;
    syscall(__NR_ioctl, r[0], 0x800000c0045002ul, 0x200000c0ul);
    break;
  case 4:
    syscall(__NR_fsetxattr, -1, 0ul, 0ul, 0ul, 0ul);
    break;
  case 5:
    *(uint64_t*)0x20000040 = 0;
    *(uint64_t*)0x20000048 = 0x10001;
    syscall(__NR_ioctl, -1, 0x4010640dul, 0x20000040ul);
    break;
  case 6:
    syscall(__NR_read, r[0], 0x20000380ul, 0x313ul);
    break;
  case 7:
    memcpy((void*)0x200002c0, "/dev/input/mouse#\000", 18);
    syz_open_dev(0x200002c0, 4, 0);
    break;
  case 8:
    syscall(__NR_socket, 2ul, 1ul, 0ul);
    break;
  case 9:
    *(uint64_t*)0x20001440 = 0;
    *(uint64_t*)0x20001448 = 0;
    *(uint64_t*)0x20001450 = 0;
    *(uint64_t*)0x20001458 = 0;
    *(uint64_t*)0x20001460 = 0x20001500;
    *(uint64_t*)0x20001468 = 0xf2;
    *(uint64_t*)0x20001470 = 0x20000080;
    *(uint64_t*)0x20001478 = 0x25;
    *(uint64_t*)0x20001480 = 0x20001600;
    *(uint64_t*)0x20001488 = 0xfd;
    *(uint64_t*)0x20001490 = 0;
    *(uint64_t*)0x20001498 = 0;
    *(uint64_t*)0x200014a0 = 0x20001700;
    *(uint64_t*)0x200014a8 = 0xb7;
    syscall(__NR_readv, r[0], 0x20001440ul, 7ul);
    break;
  }
}
int main(void)
{
  syscall(__NR_mmap, 0x20000000ul, 0x1000000ul, 3ul, 0x32ul, -1, 0);
  for (procid = 0; procid < 6; procid++) {
    if (fork() == 0) {
      loop();
    }
  }
  sleep(1000000);
  return 0;
}