report

TITLE: KMSAN: uninit-value in bpf_prog_run_generic_xdp
CORRUPTED: false ()
MAINTAINERS (TO): [davem@davemloft.net edumazet@google.com jasowang@redhat.com kuba@kernel.org netdev@vger.kernel.org pabeni@redhat.com willemdebruijn.kernel@gmail.com]
MAINTAINERS (CC): [linux-kernel@vger.kernel.org]

=====================================================
BUG: KMSAN: uninit-value in bpf_prog_run_generic_xdp+0x143d/0x1b40 net/core/dev.c:4888
 bpf_prog_run_generic_xdp+0x143d/0x1b40 net/core/dev.c:4888
 netif_receive_generic_xdp net/core/dev.c:4949 [inline]
 do_xdp_generic+0x7a5/0xb60 net/core/dev.c:5008
 tun_get_user+0x48d3/0x66b0 drivers/net/tun.c:1922
 tun_chr_write_iter+0x3bf/0x5c0 drivers/net/tun.c:2048
 call_write_iter include/linux/fs.h:2020 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x92c/0x13f0 fs/read_write.c:584
 ksys_write+0x1f3/0x4a0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x97/0xf0 fs/read_write.c:646
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
Uninit was stored to memory at:
 pskb_expand_head+0x2d1/0x19a0 net/core/skbuff.c:2142
 netif_receive_generic_xdp net/core/dev.c:4941 [inline]
 do_xdp_generic+0x4e4/0xb60 net/core/dev.c:5008
 tun_get_user+0x48d3/0x66b0 drivers/net/tun.c:1922
 tun_chr_write_iter+0x3bf/0x5c0 drivers/net/tun.c:2048
 call_write_iter include/linux/fs.h:2020 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x92c/0x13f0 fs/read_write.c:584
 ksys_write+0x1f3/0x4a0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x97/0xf0 fs/read_write.c:646
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
Uninit was created at:
 slab_post_alloc_hook+0x103/0x9e0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3478 [inline]
 __kmem_cache_alloc_node+0x5d5/0x9b0 mm/slub.c:3517
 __kmalloc_node_track_caller+0x120/0x410 mm/slab_common.c:1027
 kmalloc_reserve+0x23f/0x4a0 net/core/skbuff.c:582
 __alloc_skb+0x2fd/0x770
 alloc_skb_with_frags+0xcc/0x990 net/core/skbuff.c:6364
 sock_alloc_send_pskb+0xa65/0xbe0 net/core/sock.c:2776
 tun_build_skb drivers/net/tun.c:1693 [inline]
 tun_get_user+0x1f8b/0x66b0 drivers/net/tun.c:1819
 tun_chr_write_iter+0x3bf/0x5c0 drivers/net/tun.c:2048
 call_write_iter include/linux/fs.h:2020 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x92c/0x13f0 fs/read_write.c:584
 ksys_write+0x1f3/0x4a0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x97/0xf0 fs/read_write.c:646
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
CPU: 0 PID: 8129 Comm: e79 Not tainted 6.7.0-rc5-01538-gfc3a5534e2a8 #3
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-1.fc38 04/01/2014
=====================================================


TITLE: kernel panic: kmsan.panic set ...
CORRUPTED: false ()
MAINTAINERS (TO): [davem@davemloft.net edumazet@google.com jasowang@redhat.com kuba@kernel.org netdev@vger.kernel.org pabeni@redhat.com willemdebruijn.kernel@gmail.com]
MAINTAINERS (CC): [linux-kernel@vger.kernel.org]

 bpf_prog_run_generic_xdp+0x143d/0x1b40 net/core/dev.c:4888
 netif_receive_generic_xdp net/core/dev.c:4949 [inline]
 do_xdp_generic+0x7a5/0xb60 net/core/dev.c:5008
 tun_get_user+0x48d3/0x66b0 drivers/net/tun.c:1922
 tun_chr_write_iter+0x3bf/0x5c0 drivers/net/tun.c:2048
 call_write_iter include/linux/fs.h:2020 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x92c/0x13f0 fs/read_write.c:584
 ksys_write+0x1f3/0x4a0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x97/0xf0 fs/read_write.c:646
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
Uninit was stored to memory at:
 pskb_expand_head+0x2d1/0x19a0 net/core/skbuff.c:2142
 netif_receive_generic_xdp net/core/dev.c:4941 [inline]
 do_xdp_generic+0x4e4/0xb60 net/core/dev.c:5008
 tun_get_user+0x48d3/0x66b0 drivers/net/tun.c:1922
 tun_chr_write_iter+0x3bf/0x5c0 drivers/net/tun.c:2048
 call_write_iter include/linux/fs.h:2020 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x92c/0x13f0 fs/read_write.c:584
 ksys_write+0x1f3/0x4a0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x97/0xf0 fs/read_write.c:646
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
Uninit was created at:
 slab_post_alloc_hook+0x103/0x9e0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3478 [inline]
 __kmem_cache_alloc_node+0x5d5/0x9b0 mm/slub.c:3517
 __kmalloc_node_track_caller+0x120/0x410 mm/slab_common.c:1027
 kmalloc_reserve+0x23f/0x4a0 net/core/skbuff.c:582
 __alloc_skb+0x2fd/0x770
 alloc_skb_with_frags+0xcc/0x990 net/core/skbuff.c:6364
 sock_alloc_send_pskb+0xa65/0xbe0 net/core/sock.c:2776
 tun_build_skb drivers/net/tun.c:1693 [inline]
 tun_get_user+0x1f8b/0x66b0 drivers/net/tun.c:1819
 tun_chr_write_iter+0x3bf/0x5c0 drivers/net/tun.c:2048
 call_write_iter include/linux/fs.h:2020 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x92c/0x13f0 fs/read_write.c:584
 ksys_write+0x1f3/0x4a0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x97/0xf0 fs/read_write.c:646
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
CPU: 0 PID: 8129 Comm: e79 Not tainted 6.7.0-rc5-01538-gfc3a5534e2a8 #3
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-1.fc38 04/01/2014
=====================================================
Disabling lock debugging due to kernel taint
Kernel panic - not syncing: kmsan.panic set ...
CPU: 0 PID: 8129 Comm: e79 Tainted: G    B              6.7.0-rc5-01538-gfc3a5534e2a8 #3
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-1.fc38 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1af/0x230 lib/dump_stack.c:106
 dump_stack+0x1e/0x20 lib/dump_stack.c:113
 panic+0x4d6/0xc60
 kmsan_report+0x2d7/0x2e0 mm/kmsan/report.c:216
 __msan_warning+0x96/0x110 mm/kmsan/instrumentation.c:317
 bpf_prog_run_generic_xdp+0x143d/0x1b40 net/core/dev.c:4888
 netif_receive_generic_xdp net/core/dev.c:4949 [inline]
 do_xdp_generic+0x7a5/0xb60 net/core/dev.c:5008
 tun_get_user+0x48d3/0x66b0 drivers/net/tun.c:1922
 tun_chr_write_iter+0x3bf/0x5c0 drivers/net/tun.c:2048
 call_write_iter include/linux/fs.h:2020 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x92c/0x13f0 fs/read_write.c:584
 ksys_write+0x1f3/0x4a0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x97/0xf0 fs/read_write.c:646
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x436cf0
Code: 40 00 48 c7 c2 b8 ff ff ff f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 80 3d b1 83 07 009
RSP: 002b:00007fff3f6713c8 EFLAGS: 00000202 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000020000f0c RCX: 0000000000436cf0
RDX: 000000000000fdef RSI: 0000000020000f00 RDI: 00000000000000c8
RBP: 00007fff3f671400 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000001
R13: 00007fff3f671658 R14: 0000000000000001 R15: 0000000000000001
 </TASK>

repro.c

// 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 <linux/capability.h>
#include <linux/genetlink.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>
#include <net/if.h>
#include <net/if_arp.h>
#include <netinet/in.h>
#include <sched.h>
#include <signal.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/uio.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>

#ifndef __NR_bpf
#define __NR_bpf 321
#endif

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 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[4096];
};

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;
  if (size > 0) 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, bool dofail) {
  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;
  ssize_t n = sendto(sock, nlmsg->buf, hdr->nlmsg_len, 0,
                     (struct sockaddr*)&addr, sizeof(addr));
  if (n != (ssize_t)hdr->nlmsg_len) {
    if (dofail) exit(1);
    return -1;
  }
  n = recv(sock, nlmsg->buf, sizeof(nlmsg->buf), 0);
  if (reply_len) *reply_len = 0;
  if (n < 0) {
    if (dofail) exit(1);
    return -1;
  }
  if (n < (ssize_t)sizeof(struct nlmsghdr)) {
    errno = EINVAL;
    if (dofail) exit(1);
    return -1;
  }
  if (hdr->nlmsg_type == NLMSG_DONE) return 0;
  if (reply_len && hdr->nlmsg_type == reply_type) {
    *reply_len = n;
    return 0;
  }
  if (n < (ssize_t)(sizeof(struct nlmsghdr) + sizeof(struct nlmsgerr))) {
    errno = EINVAL;
    if (dofail) exit(1);
    return -1;
  }
  if (hdr->nlmsg_type != NLMSG_ERROR) {
    errno = EINVAL;
    if (dofail) exit(1);
    return -1;
  }
  errno = -((struct nlmsgerr*)(hdr + 1))->error;
  return -errno;
}

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

static int netlink_query_family_id(struct nlmsg* nlmsg, int sock,
                                   const char* family_name, bool dofail) {
  struct genlmsghdr genlhdr;
  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, family_name,
               strnlen(family_name, GENL_NAMSIZ - 1) + 1);
  int n = 0;
  int err = netlink_send_ext(nlmsg, sock, GENL_ID_CTRL, &n, dofail);
  if (err < 0) {
    return -1;
  }
  uint16_t id = 0;
  struct nlattr* 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) {
    errno = EINVAL;
    return -1;
  }
  recv(sock, nlmsg->buf, sizeof(nlmsg->buf), 0);
  return id;
}

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);
  if (err < 0) {
  }
}

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));
  if (err < 0) {
  }
}

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));
  if (err < 0) {
  }
}

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);
  if (err < 0) {
  }
}

static struct nlmsg nlmsg;

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 = 200;
  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 int read_tun(char* data, int size) {
  if (tunfd < 0) return -1;
  int rv = read(tunfd, data, size);
  if (rv < 0) {
    if (errno == EAGAIN || errno == EBADFD) return -1;
    exit(1);
  }
  return rv;
}

static long syz_emit_ethernet(volatile long a0, volatile long a1,
                              volatile long a2) {
  if (tunfd < 0) return (uintptr_t)-1;
  uint32_t length = a0;
  char* data = (char*)a1;
  return write(tunfd, data, length);
}

static void flush_tun() {
  char data[1000];
  while (read_tun(&data[0], sizeof(data)) != -1) {
  }
}

#define MAX_FDS 30

static void setup_common() {
  if (mount(0, "/sys/fs/fuse/connections", "fusectl", 0, 0)) {
  }
}

static void setup_binderfs() {
  if (mkdir("/dev/binderfs", 0777)) {
  }
  if (mount("binder", "/dev/binderfs", "binder", 0, NULL)) {
  }
  if (symlink("/dev/binderfs", "./binderfs")) {
  }
}

static void loop();

static void sandbox_common() {
  prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
  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 = 128 << 20;
  setrlimit(RLIMIT_CORE, &rlim);
  rlim.rlim_cur = rlim.rlim_max = 256;
  setrlimit(RLIMIT_NOFILE, &rlim);
  if (unshare(CLONE_NEWNS)) {
  }
  if (mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, NULL)) {
  }
  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)) {
  }
  write_file("/proc/sys/net/ipv4/ping_group_range", "0 65535");
  initialize_tun();
  setup_binderfs();
  loop();
  exit(1);
}

static void kill_and_wait(int pid, int* status) {
  kill(-pid, SIGKILL);
  kill(pid, SIGKILL);
  for (int 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");
  flush_tun();
}

static void close_fds() {
  for (int fd = 3; fd < MAX_FDS; fd++) close(fd);
}

static void execute_one(void);

#define WAIT_FLAGS __WALL

static void loop(void) {
  int iter = 0;
  for (;; iter++) {
    int pid = fork();
    if (pid < 0) exit(1);
    if (pid == 0) {
      setup_test();
      execute_one();
      close_fds();
      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 < 5000) continue;
      kill_and_wait(pid, &status);
      break;
    }
  }
}

uint64_t r[3] = {0xffffffffffffffff, 0xffffffffffffffff, 0x0};

void execute_one(void) {
  intptr_t res = 0;
  res = syscall(__NR_socket, /*domain=*/2ul, /*type=*/1ul, /*proto=*/0);
  if (res != -1) r[0] = res;
  *(uint32_t*)0x20000100 = 6;
  *(uint32_t*)0x20000104 = 4;
  *(uint64_t*)0x20000108 = 0x20000200;
  memcpy((void*)0x20000200,
         "\x18\x02\x00\x00\xfd\xff\xff\xff\x00\x00\x00\x00\x00\x00\x00\x00\x85"
         "\x00\x00\x00\x2c\x00\x00\x00\x95",
         25);
  *(uint64_t*)0x20000110 = 0x20000040;
  memcpy((void*)0x20000040, "GPL\000", 4);
  *(uint32_t*)0x20000118 = 0;
  *(uint32_t*)0x2000011c = 0;
  *(uint64_t*)0x20000120 = 0;
  *(uint32_t*)0x20000128 = 0;
  *(uint32_t*)0x2000012c = 0;
  memset((void*)0x20000130, 0, 16);
  *(uint32_t*)0x20000140 = 0;
  *(uint32_t*)0x20000144 = 0;
  *(uint32_t*)0x20000148 = -1;
  *(uint32_t*)0x2000014c = 8;
  *(uint64_t*)0x20000150 = 0;
  *(uint32_t*)0x20000158 = 0;
  *(uint32_t*)0x2000015c = 0x10;
  *(uint64_t*)0x20000160 = 0;
  *(uint32_t*)0x20000168 = 0;
  *(uint32_t*)0x2000016c = 0;
  *(uint32_t*)0x20000170 = 0;
  *(uint32_t*)0x20000174 = 0;
  *(uint64_t*)0x20000178 = 0;
  *(uint64_t*)0x20000180 = 0;
  *(uint32_t*)0x20000188 = 0x10;
  *(uint32_t*)0x2000018c = 0;
  res = syscall(__NR_bpf, /*cmd=*/5ul, /*arg=*/0x20000100ul, /*size=*/0x90ul);
  if (res != -1) r[1] = res;
  memcpy((void*)0x20000180, "syz_tun\000\000\000\000\000\000\000\000\000", 16);
  res = syscall(__NR_ioctl, /*fd=*/r[0], /*cmd=*/0x8933, /*arg=*/0x20000180ul);
  if (res != -1) r[2] = *(uint32_t*)0x20000190;
  *(uint32_t*)0x20000000 = r[1];
  *(uint32_t*)0x20000004 = r[2];
  *(uint32_t*)0x20000008 = 0x25;
  *(uint32_t*)0x2000000c = 0;
  *(uint32_t*)0x20000010 = 0;
  syscall(__NR_bpf, /*cmd=*/0x1cul, /*arg=*/0x20000000ul, /*size=*/0x10ul);
  memset((void*)0x20000f00, 170, 5);
  *(uint8_t*)0x20000f05 = 0xaa;
  memset((void*)0x20000f06, 0, 6);
  *(uint16_t*)0x20000f0c = htobe16(0);
  syz_emit_ethernet(/*len=*/0xfdef, /*packet=*/0x20000f00, /*frags=*/0);
}
int main(void) {
  syscall(__NR_mmap, /*addr=*/0x1ffff000ul, /*len=*/0x1000ul, /*prot=*/0ul,
          /*flags=*/0x32ul, /*fd=*/-1, /*offset=*/0ul);
  syscall(__NR_mmap, /*addr=*/0x20000000ul, /*len=*/0x1000000ul, /*prot=*/7ul,
          /*flags=*/0x32ul, /*fd=*/-1, /*offset=*/0ul);
  syscall(__NR_mmap, /*addr=*/0x21000000ul, /*len=*/0x1000ul, /*prot=*/0ul,
          /*flags=*/0x32ul, /*fd=*/-1, /*offset=*/0ul);
  do_sandbox_none();
  return 0;
}

repro.txt

r0 = socket$inet_tcp(0x2, 0x1, 0x0)
r1 = bpf$BPF_PROG_RAW_TRACEPOINT_LOAD(0x5, &(0x7f0000000100)={0x6, 0x4, &(0x7f0000000200)=ANY=[@ANYBLOB="18020000fdffffff0000000000000000850000002c00000095"], &(0x7f0000000040)='GPL\x00'}, 0x90)
ioctl$sock_SIOCGIFINDEX(r0, 0x8933, &(0x7f0000000180)={'syz_tun\x00', <r2=>0x0})
bpf$BPF_LINK_CREATE_XDP(0x1c, &(0x7f0000000000)={r1, r2}, 0x10)
syz_emit_ethernet(0xfdef, &(0x7f0000000f00)={@local, @empty, @void}, 0x0)