diff --git a/tools/test/stress2/misc/syzkaller56.sh b/tools/test/stress2/misc/syzkaller56.sh
new file mode 100755
index 000000000000..f24dafa72823
--- /dev/null
+++ b/tools/test/stress2/misc/syzkaller56.sh
@@ -0,0 +1,298 @@
+#!/bin/sh
+
+# panic: Assertion clen >= sizeof(*cm) && clen <= cm->cmsg_len failed at ../../../kern/uipc_usrreq.c:2018
+# cpuid = 8
+# time = 1653654831
+# KDB: stack backtrace:
+# db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe0158aebaa0
+# vpanic() at vpanic+0x17f/frame 0xfffffe0158aebaf0
+# panic() at panic+0x43/frame 0xfffffe0158aebb50
+# unp_externalize() at unp_externalize+0x3b7/frame 0xfffffe0158aebbe0
+# soreceive_generic() at soreceive_generic+0x73d/frame 0xfffffe0158aebca0
+# soreceive() at soreceive+0x4b/frame 0xfffffe0158aebcc0
+# kern_recvit() at kern_recvit+0x1ba/frame 0xfffffe0158aebd70
+# sys_recvfrom() at sys_recvfrom+0x95/frame 0xfffffe0158aebe00
+# amd64_syscall() at amd64_syscall+0x145/frame 0xfffffe0158aebf30
+# fast_syscall_common() at fast_syscall_common+0xf8/frame 0xfffffe0158aebf30
+# --- syscall (0, FreeBSD ELF64, nosys), rip = 0x8230797da, rsp = 0x827bc4f48, rbp = 0x827bc4f70 ---
+# KDB: enter: panic
+# [ thread pid 32490 tid 141239 ]
+# Stopped at      78043(%rip)
+# db> x/s version
+# FreeBSD 14.0-CURRENT #0 n255820-4682ac697ce9b: Fri May 27 07:06:21 CEST 2022
+# pho@mercat1.netperf.freebsd.org:/usr/src/sys/amd64/compile/PHO
+# db> 
+
+
+[ `uname -p` != "amd64" ] && exit 0
+
+. ../default.cfg
+cat > /tmp/syzkaller56.c <<EOF
+// https://syzkaller.appspot.com/bug?id=10ad96d3c8f58f42ad73650e339a4952f9d82254
+// autogenerated by syzkaller (https://github.com/google/syzkaller)
+// Reported-by: syzbot+c48c62e7fbd8ef327088@syzkaller.appspotmail.com
+
+#define _GNU_SOURCE
+
+#include <errno.h>
+#include <pthread.h>
+#include <pwd.h>
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/endian.h>
+#include <sys/syscall.h>
+#include <time.h>
+#include <unistd.h>
+
+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 = 0;
+  for (; 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);
+}
+
+typedef struct {
+  pthread_mutex_t mu;
+  pthread_cond_t cv;
+  int state;
+} event_t;
+
+static void event_init(event_t* ev)
+{
+  if (pthread_mutex_init(&ev->mu, 0))
+    exit(1);
+  if (pthread_cond_init(&ev->cv, 0))
+    exit(1);
+  ev->state = 0;
+}
+
+static void event_reset(event_t* ev)
+{
+  ev->state = 0;
+}
+
+static void event_set(event_t* ev)
+{
+  pthread_mutex_lock(&ev->mu);
+  if (ev->state)
+    exit(1);
+  ev->state = 1;
+  pthread_mutex_unlock(&ev->mu);
+  pthread_cond_broadcast(&ev->cv);
+}
+
+static void event_wait(event_t* ev)
+{
+  pthread_mutex_lock(&ev->mu);
+  while (!ev->state)
+    pthread_cond_wait(&ev->cv, &ev->mu);
+  pthread_mutex_unlock(&ev->mu);
+}
+
+static int event_isset(event_t* ev)
+{
+  pthread_mutex_lock(&ev->mu);
+  int res = ev->state;
+  pthread_mutex_unlock(&ev->mu);
+  return res;
+}
+
+static int event_timedwait(event_t* ev, uint64_t timeout)
+{
+  uint64_t start = current_time_ms();
+  uint64_t now = start;
+  pthread_mutex_lock(&ev->mu);
+  for (;;) {
+    if (ev->state)
+      break;
+    uint64_t remain = timeout - (now - start);
+    struct timespec ts;
+    ts.tv_sec = remain / 1000;
+    ts.tv_nsec = (remain % 1000) * 1000 * 1000;
+    pthread_cond_timedwait(&ev->cv, &ev->mu, &ts);
+    now = current_time_ms();
+    if (now - start > timeout)
+      break;
+  }
+  int res = ev->state;
+  pthread_mutex_unlock(&ev->mu);
+  return res;
+}
+
+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 < 3; 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, 50);
+      break;
+    }
+  }
+  for (i = 0; i < 100 && __atomic_load_n(&running, __ATOMIC_RELAXED); i++)
+    sleep_ms(1);
+}
+
+uint64_t r[2] = {0xffffffffffffffff, 0xffffffffffffffff};
+
+void execute_call(int call)
+{
+  intptr_t res = 0;
+  switch (call) {
+  case 0:
+    res = syscall(SYS_socketpair, 1ul, 5ul, 0, 0x20000100ul);
+    if (res != -1) {
+      r[0] = *(uint32_t*)0x20000100;
+      r[1] = *(uint32_t*)0x20000104;
+    }
+    break;
+  case 1:
+    syscall(SYS_recvfrom, r[0], 0x20000140ul, 0x1000ul, 0ul, 0ul, 0ul);
+    break;
+  case 2:
+    *(uint64_t*)0x20001e40 = 0;
+    *(uint32_t*)0x20001e48 = 0;
+    *(uint64_t*)0x20001e50 = 0;
+    *(uint64_t*)0x20001e58 = 0;
+    *(uint64_t*)0x20001e60 = 0x20001f80;
+    memcpy((void*)0x20001f80,
+           "\x60\x00\x00\x00\xff\xff\x00\x00\x03\x00\x00\x00", 12);
+    *(uint32_t*)0x20001f8c = -1;
+    *(uint32_t*)0x20001f90 = 0;
+    *(uint32_t*)0x20001f94 = 0;
+    *(uint32_t*)0x20001f98 = 0;
+    memcpy((void*)0x20001f9c, "\x10\x00\x26\x00", 4);
+    *(uint32_t*)0x20001fa0 = 0;
+    *(uint32_t*)0x20001fa4 = 0;
+    *(uint32_t*)0x20001fa8 = 0;
+    *(uint32_t*)0x20001fac = 0;
+    *(uint32_t*)0x20001fb0 = 0;
+    *(uint32_t*)0x20001fb4 = 0;
+    *(uint32_t*)0x20001fb8 = -1;
+    *(uint32_t*)0x20001fbc = 0;
+    *(uint32_t*)0x20001fc0 = -1;
+    *(uint32_t*)0x20001fc4 = 0;
+    *(uint32_t*)0x20001fc8 = 0;
+    *(uint32_t*)0x20001fcc = 0;
+    *(uint32_t*)0x20001fd0 = 0;
+    *(uint32_t*)0x20001fd4 = 0;
+    *(uint32_t*)0x20001fd8 = 0;
+    *(uint32_t*)0x20001fdc = 0;
+    memcpy((void*)0x20001fe0,
+           "\x60\x00\x00\x00\xff\xff\x00\x00\x03\x00\x00\x00", 12);
+    *(uint32_t*)0x20001fec = 0;
+    *(uint32_t*)0x20001ff0 = 0;
+    *(uint32_t*)0x20001ff4 = 0;
+    *(uint32_t*)0x20001ff8 = -1;
+    memcpy((void*)0x20001ffc, "\x10\x00\x00\x00", 4);
+    *(uint32_t*)0x20002000 = -1;
+    *(uint32_t*)0x20002004 = 0;
+    *(uint32_t*)0x20002008 = 0;
+    *(uint32_t*)0x2000200c = 0;
+    *(uint32_t*)0x20002010 = 0;
+    *(uint32_t*)0x20002014 = 0;
+    *(uint32_t*)0x20002018 = -1;
+    *(uint32_t*)0x2000201c = 0;
+    *(uint32_t*)0x20002020 = -1;
+    *(uint32_t*)0x20002024 = 0;
+    *(uint32_t*)0x20002028 = 0;
+    *(uint32_t*)0x2000202c = 0;
+    *(uint32_t*)0x20002030 = 0;
+    *(uint32_t*)0x20002034 = 0;
+    *(uint32_t*)0x20002038 = 0;
+    *(uint32_t*)0x2000203c = -1;
+    memcpy((void*)0x20002040,
+           "\x14\x00\x00\x00\xff\xff\x00\x00\x01\x00\x00\x00", 12);
+    *(uint32_t*)0x2000204c = -1;
+    *(uint32_t*)0x20002050 = r[1];
+    *(uint64_t*)0x20001e68 = 0xd4;
+    *(uint32_t*)0x20001e70 = 0;
+    syscall(SYS_sendmsg, r[1], 0x20001e40ul, 0ul);
+    break;
+  }
+}
+int main(void)
+{
+  syscall(SYS_mmap, 0x20000000ul, 0x1000000ul, 7ul, 0x1012ul, -1, 0ul);
+  loop();
+  return 0;
+}
+EOF
+mycc -o /tmp/syzkaller56 -Wall -Wextra -O0 /tmp/syzkaller56.c -lpthread ||
+    exit 1
+
+start=`date +%s`
+while [ $((`date +%s` - start)) -lt 60 ]; do
+	(cd /tmp; timeout 3m ./syzkaller56)
+done
+
+rm -rf /tmp/syzkaller56 /tmp/syzkaller56.c /tmp/syzkaller56.core \
+    /tmp/syzkaller.??????
+exit 0