text: // KASAN: use-after-free Read in __ext4_check_dir_entry
  // https://syzkaller.appspot.com/bug?id=b525c860dd8b07d5903f
  // status:0
  // autogenerated by syzkaller (https://github.com/google/syzkaller)
  
  #define _GNU_SOURCE
  
  #include <arpa/inet.h>
  #include <endian.h>
  #include <errno.h>
  #include <fcntl.h>
  #include <net/if.h>
  #include <net/if_arp.h>
  #include <netinet/in.h>
  #include <sched.h>
  #include <stdarg.h>
  #include <stdbool.h>
  #include <stdint.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <sys/ioctl.h>
  #include <sys/mount.h>
  #include <sys/prctl.h>
  #include <sys/resource.h>
  #include <sys/socket.h>
  #include <sys/stat.h>
  #include <sys/syscall.h>
  #include <sys/time.h>
  #include <sys/types.h>
  #include <sys/wait.h>
  #include <unistd.h>
  
  #include <linux/capability.h>
  #include <linux/if_addr.h>
  #include <linux/if_ether.h>
  #include <linux/if_link.h>
  #include <linux/if_tun.h>
  #include <linux/in6.h>
  #include <linux/ip.h>
  #include <linux/neighbour.h>
  #include <linux/net.h>
  #include <linux/netlink.h>
  #include <linux/rtnetlink.h>
  #include <linux/tcp.h>
  #include <linux/veth.h>
  
  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 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;
  }
  
  static int netlink_add_addr(struct nlmsg* nlmsg, int sock, const char* dev,
                              const void* addr, int addrsize)
  {
    struct ifaddrmsg hdr;
    memset(&hdr, 0, sizeof(hdr));
    hdr.ifa_family = addrsize == 4 ? AF_INET : AF_INET6;
    hdr.ifa_prefixlen = addrsize == 4 ? 24 : 120;
    hdr.ifa_scope = RT_SCOPE_UNIVERSE;
    hdr.ifa_index = if_nametoindex(dev);
    netlink_init(nlmsg, RTM_NEWADDR, NLM_F_CREATE | NLM_F_REPLACE, &hdr,
                 sizeof(hdr));
    netlink_attr(nlmsg, IFA_LOCAL, addr, addrsize);
    netlink_attr(nlmsg, IFA_ADDRESS, addr, addrsize);
    return netlink_send(nlmsg, sock);
  }
  
  static void netlink_add_addr4(struct nlmsg* nlmsg, int sock, const char* dev,
                                const char* addr)
  {
    struct in_addr in_addr;
    inet_pton(AF_INET, addr, &in_addr);
    int err = netlink_add_addr(nlmsg, sock, dev, &in_addr, sizeof(in_addr));
    (void)err;
  }
  
  static void netlink_add_addr6(struct nlmsg* nlmsg, int sock, const char* dev,
                                const char* addr)
  {
    struct in6_addr in6_addr;
    inet_pton(AF_INET6, addr, &in6_addr);
    int err = netlink_add_addr(nlmsg, sock, dev, &in6_addr, sizeof(in6_addr));
    (void)err;
  }
  
  static void netlink_add_neigh(struct nlmsg* nlmsg, int sock, const char* name,
                                const void* addr, int addrsize, const void* mac,
                                int macsize)
  {
    struct ndmsg hdr;
    memset(&hdr, 0, sizeof(hdr));
    hdr.ndm_family = addrsize == 4 ? AF_INET : AF_INET6;
    hdr.ndm_ifindex = if_nametoindex(name);
    hdr.ndm_state = NUD_PERMANENT;
    netlink_init(nlmsg, RTM_NEWNEIGH, NLM_F_EXCL | NLM_F_CREATE, &hdr,
                 sizeof(hdr));
    netlink_attr(nlmsg, NDA_DST, addr, addrsize);
    netlink_attr(nlmsg, NDA_LLADDR, mac, macsize);
    int err = netlink_send(nlmsg, sock);
    (void)err;
  }
  
  static int tunfd = -1;
  
  #define TUN_IFACE "syz_tun"
  #define LOCAL_MAC 0xaaaaaaaaaaaa
  #define REMOTE_MAC 0xaaaaaaaaaabb
  #define LOCAL_IPV4 "172.20.20.170"
  #define REMOTE_IPV4 "172.20.20.187"
  #define LOCAL_IPV6 "fe80::aa"
  #define REMOTE_IPV6 "fe80::bb"
  
  #define IFF_NAPI 0x0010
  
  static void initialize_tun(void)
  {
    tunfd = open("/dev/net/tun", O_RDWR | O_NONBLOCK);
    if (tunfd == -1) {
      printf("tun: can't open /dev/net/tun: please enable CONFIG_TUN=y\n");
      printf("otherwise fuzzing or reproducing might not work as intended\n");
      return;
    }
    const int kTunFd = 240;
    if (dup2(tunfd, kTunFd) < 0)
      exit(1);
    close(tunfd);
    tunfd = kTunFd;
    struct ifreq ifr;
    memset(&ifr, 0, sizeof(ifr));
    strncpy(ifr.ifr_name, TUN_IFACE, IFNAMSIZ);
    ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
    if (ioctl(tunfd, TUNSETIFF, (void*)&ifr) < 0) {
      exit(1);
    }
    char sysctl[64];
    sprintf(sysctl, "/proc/sys/net/ipv6/conf/%s/accept_dad", TUN_IFACE);
    write_file(sysctl, "0");
    sprintf(sysctl, "/proc/sys/net/ipv6/conf/%s/router_solicitations", TUN_IFACE);
    write_file(sysctl, "0");
    int sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
    if (sock == -1)
      exit(1);
    netlink_add_addr4(&nlmsg, sock, TUN_IFACE, LOCAL_IPV4);
    netlink_add_addr6(&nlmsg, sock, TUN_IFACE, LOCAL_IPV6);
    uint64_t macaddr = REMOTE_MAC;
    struct in_addr in_addr;
    inet_pton(AF_INET, REMOTE_IPV4, &in_addr);
    netlink_add_neigh(&nlmsg, sock, TUN_IFACE, &in_addr, sizeof(in_addr),
                      &macaddr, ETH_ALEN);
    struct in6_addr in6_addr;
    inet_pton(AF_INET6, REMOTE_IPV6, &in6_addr);
    netlink_add_neigh(&nlmsg, sock, TUN_IFACE, &in6_addr, sizeof(in6_addr),
                      &macaddr, ETH_ALEN);
    macaddr = LOCAL_MAC;
    netlink_device_change(&nlmsg, sock, TUN_IFACE, true, 0, &macaddr, ETH_ALEN,
                          NULL);
    close(sock);
  }
  
  static long syz_open_procfs(volatile long a0, volatile long a1)
  {
    char buf[128];
    memset(buf, 0, sizeof(buf));
    if (a0 == 0) {
      snprintf(buf, sizeof(buf), "/proc/self/%s", (char*)a1);
    } else if (a0 == -1) {
      snprintf(buf, sizeof(buf), "/proc/thread-self/%s", (char*)a1);
    } else {
      snprintf(buf, sizeof(buf), "/proc/self/task/%d/%s", (int)a0, (char*)a1);
    }
    int fd = open(buf, O_RDWR);
    if (fd == -1)
      fd = open(buf, O_RDONLY);
    return fd;
  }
  
  static void setup_common()
  {
    if (mount(0, "/sys/fs/fuse/connections", "fusectl", 0, 0)) {
    }
  }
  
  static void loop();
  
  static void sandbox_common()
  {
    prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
    setpgrp();
    setsid();
    struct rlimit rlim;
    rlim.rlim_cur = rlim.rlim_max = (200 << 20);
    setrlimit(RLIMIT_AS, &rlim);
    rlim.rlim_cur = rlim.rlim_max = 32 << 20;
    setrlimit(RLIMIT_MEMLOCK, &rlim);
    rlim.rlim_cur = rlim.rlim_max = 136 << 20;
    setrlimit(RLIMIT_FSIZE, &rlim);
    rlim.rlim_cur = rlim.rlim_max = 1 << 20;
    setrlimit(RLIMIT_STACK, &rlim);
    rlim.rlim_cur = rlim.rlim_max = 0;
    setrlimit(RLIMIT_CORE, &rlim);
    rlim.rlim_cur = rlim.rlim_max = 256;
    setrlimit(RLIMIT_NOFILE, &rlim);
    if (unshare(CLONE_NEWNS)) {
    }
    if (unshare(CLONE_NEWIPC)) {
    }
    if (unshare(0x02000000)) {
    }
    if (unshare(CLONE_NEWUTS)) {
    }
    if (unshare(CLONE_SYSVSEM)) {
    }
    typedef struct {
      const char* name;
      const char* value;
    } sysctl_t;
    static const sysctl_t sysctls[] = {
        {"/proc/sys/kernel/shmmax", "16777216"},
        {"/proc/sys/kernel/shmall", "536870912"},
        {"/proc/sys/kernel/shmmni", "1024"},
        {"/proc/sys/kernel/msgmax", "8192"},
        {"/proc/sys/kernel/msgmni", "1024"},
        {"/proc/sys/kernel/msgmnb", "1024"},
        {"/proc/sys/kernel/sem", "1024 1048576 500 1024"},
    };
    unsigned i;
    for (i = 0; i < sizeof(sysctls) / sizeof(sysctls[0]); i++)
      write_file(sysctls[i].name, sysctls[i].value);
  }
  
  static int wait_for_loop(int pid)
  {
    if (pid < 0)
      exit(1);
    int status = 0;
    while (waitpid(-1, &status, __WALL) != pid) {
    }
    return WEXITSTATUS(status);
  }
  
  static void drop_caps(void)
  {
    struct __user_cap_header_struct cap_hdr = {};
    struct __user_cap_data_struct cap_data[2] = {};
    cap_hdr.version = _LINUX_CAPABILITY_VERSION_3;
    cap_hdr.pid = getpid();
    if (syscall(SYS_capget, &cap_hdr, &cap_data))
      exit(1);
    const int drop = (1 << CAP_SYS_PTRACE) | (1 << CAP_SYS_NICE);
    cap_data[0].effective &= ~drop;
    cap_data[0].permitted &= ~drop;
    cap_data[0].inheritable &= ~drop;
    if (syscall(SYS_capset, &cap_hdr, &cap_data))
      exit(1);
  }
  
  static int do_sandbox_none(void)
  {
    if (unshare(CLONE_NEWPID)) {
    }
    int pid = fork();
    if (pid != 0)
      return wait_for_loop(pid);
    setup_common();
    sandbox_common();
    drop_caps();
    if (unshare(CLONE_NEWNET)) {
    }
    initialize_tun();
    loop();
    exit(1);
  }
  
  uint64_t r[1] = {0xffffffffffffffff};
  
  void loop(void)
  {
    intptr_t res = 0;
    *(uint32_t*)0x20000040 = 9;
    *(uint32_t*)0x20000044 = 1;
    memcpy((void*)0x20000048, "\v", 1);
    syscall(__NR_open_by_handle_at, 0xffffff9c, 0x20000040ul, 0ul);
    memcpy((void*)0x200000c0, "fd/3\000", 5);
    res = syz_open_procfs(0, 0x200000c0);
    if (res != -1)
      r[0] = res;
    syscall(__NR_lseek, r[0], 0xfffffffffffffffdul, 2ul);
    syscall(__NR_getdents64, r[0], 0ul, 0ul);
  }
  int main(void)
  {
    syscall(__NR_mmap, 0x1ffff000ul, 0x1000ul, 0ul, 0x32ul, -1, 0ul);
    syscall(__NR_mmap, 0x20000000ul, 0x1000000ul, 7ul, 0x32ul, -1, 0ul);
    syscall(__NR_mmap, 0x21000000ul, 0x1000ul, 0ul, 0x32ul, -1, 0ul);
    do_sandbox_none();
    return 0;
  }
  