report

general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 3 PID: 19805 Comm: syz-executor.2 Not tainted 6.7.0-rc4-00141-g1ae4cd3cbdd0-dirty #5
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:ccid_hc_tx_send_packet net/dccp/ccid.h:166 [inline]
RIP: 0010:dccp_write_xmit+0x74/0x240 net/dccp/output.c:356
Code: 03 48 89 44 24 08 4c 89 2c 24 48 8b 44 24 08 80 3c 28 00 74 08 48 89 df e8 79 dc a7 f7 49 89 df 48 8b 1b 48 89 d8 48 c1 e8 03 <80> 3c 28 00 74 08 48 89 df e8 5e dc a7 f7 48 8b 1b b8 b0 00 00 00
RSP: 0018:ffffc900061e7758 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff8881045ad400
RDX: ffffffff8a494702 RSI: 0000000000000000 RDI: 0000000000000001
RBP: dffffc0000000000 R08: 0000000000000cf5 R09: 0000000000000cf6
R10: dffffc0000000000 R11: fffffbfff2169e87 R12: ffff8881045ad400
R13: ffff88810629c080 R14: ffff88810629c9d0 R15: ffff88810629c970
FS:  00007f2a1785f6c0(0000) GS:ffff888135d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f51c5d9ad58 CR3: 000000001f1dc000 CR4: 0000000000350ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 dccp_sendmsg+0x784/0xba0 net/dccp/proto.c:801
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 ____sys_sendmsg+0x5aa/0x8b0 net/socket.c:2584
 ___sys_sendmsg net/socket.c:2638 [inline]
 __sys_sendmmsg+0x3c1/0x760 net/socket.c:2724
 __do_sys_sendmmsg net/socket.c:2753 [inline]
 __se_sys_sendmmsg net/socket.c:2750 [inline]
 __x64_sys_sendmmsg+0xa5/0xc0 net/socket.c:2750
 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: 0033:0x7f2a16a7cb29
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2a1785f0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f2a16b9c1f0 RCX: 00007f2a16a7cb29
RDX: 0000000000000001 RSI: 0000000020000200 RDI: 0000000000000007
RBP: 00007f2a16ac847a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000048000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000006e R14: 00007f2a16b9c1f0 R15: 00007ffd3c4d9b98
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ccid_hc_tx_send_packet net/dccp/ccid.h:166 [inline]
RIP: 0010:dccp_write_xmit+0x74/0x240 net/dccp/output.c:356
Code: 03 48 89 44 24 08 4c 89 2c 24 48 8b 44 24 08 80 3c 28 00 74 08 48 89 df e8 79 dc a7 f7 49 89 df 48 8b 1b 48 89 d8 48 c1 e8 03 <80> 3c 28 00 74 08 48 89 df e8 5e dc a7 f7 48 8b 1b b8 b0 00 00 00
RSP: 0018:ffffc900061e7758 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff8881045ad400
RDX: ffffffff8a494702 RSI: 0000000000000000 RDI: 0000000000000001
RBP: dffffc0000000000 R08: 0000000000000cf5 R09: 0000000000000cf6
R10: dffffc0000000000 R11: fffffbfff2169e87 R12: ffff8881045ad400
R13: ffff88810629c080 R14: ffff88810629c9d0 R15: ffff88810629c970
FS:  00007f2a1785f6c0(0000) GS:ffff888135d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f51c5d9ad58 CR3: 000000001f1dc000 CR4: 0000000000350ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	03 48 89             	add    -0x77(%rax),%ecx
   3:	44 24 08             	rex.R and $0x8,%al
   6:	4c 89 2c 24          	mov    %r13,(%rsp)
   a:	48 8b 44 24 08       	mov    0x8(%rsp),%rax
   f:	80 3c 28 00          	cmpb   $0x0,(%rax,%rbp,1)
  13:	74 08                	je     0x1d
  15:	48 89 df             	mov    %rbx,%rdi
  18:	e8 79 dc a7 f7       	call   0xf7a7dc96
  1d:	49 89 df             	mov    %rbx,%r15
  20:	48 8b 1b             	mov    (%rbx),%rbx
  23:	48 89 d8             	mov    %rbx,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	80 3c 28 00          	cmpb   $0x0,(%rax,%rbp,1) <-- trapping instruction
  2e:	74 08                	je     0x38
  30:	48 89 df             	mov    %rbx,%rdi
  33:	e8 5e dc a7 f7       	call   0xf7a7dc96
  38:	48 8b 1b             	mov    (%rbx),%rbx
  3b:	b8 b0 00 00 00       	mov    $0xb0,%eax

repro.c

// autogenerated by syzkaller (https://github.com/google/syzkaller)

#define _GNU_SOURCE

#include <dirent.h>
#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <linux/futex.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/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/wait.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 {
  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, 1000000);
}

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_ACQUIRE)) 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;
}

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");
}

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;
  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);
      event_timedwait(&th->done, 50);
      break;
    }
  }
  for (i = 0; i < 100 && __atomic_load_n(&running, __ATOMIC_RELAXED); i++)
    sleep_ms(1);
}

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();
      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[5] = {0xffffffffffffffff, 0xffffffffffffffff, 0x0,
                 0xffffffffffffffff, 0xffffffffffffffff};

void execute_call(int call) {
  intptr_t res = 0;
  switch (call) {
    case 0:
      res = syscall(__NR_socket, /*domain=*/0x10ul, /*type=*/0x803ul,
                    /*proto=*/0);
      if (res != -1) r[0] = res;
      break;
    case 1:
      res = syscall(__NR_socket, /*domain=*/0xaul, /*type=*/1ul, /*proto=*/0);
      if (res != -1) r[1] = res;
      break;
    case 2:
      memcpy((void*)0x200001c0,
             "wg1\000\000\000\000\000\000\000\000\000\000\000\000\000", 16);
      res = syscall(__NR_ioctl, /*fd=*/r[1], /*cmd=*/0x8933,
                    /*arg=*/0x200001c0ul);
      if (res != -1) r[2] = *(uint32_t*)0x200001d0;
      break;
    case 3:
      *(uint64_t*)0x20000340 = 0;
      *(uint32_t*)0x20000348 = 0;
      *(uint64_t*)0x20000350 = 0x20002840;
      *(uint64_t*)0x20002840 = 0x20000080;
      *(uint32_t*)0x20000080 = 0x2c;
      *(uint16_t*)0x20000084 = 0x14;
      *(uint16_t*)0x20000086 = 1;
      *(uint32_t*)0x20000088 = 0;
      *(uint32_t*)0x2000008c = 0;
      *(uint8_t*)0x20000090 = 0xa;
      *(uint8_t*)0x20000091 = 0;
      *(uint8_t*)0x20000092 = 0;
      *(uint8_t*)0x20000093 = 0;
      *(uint32_t*)0x20000094 = r[2];
      *(uint16_t*)0x20000098 = 0x14;
      *(uint16_t*)0x2000009a = 2;
      *(uint8_t*)0x2000009c = 0xfe;
      *(uint8_t*)0x2000009d = 0x80;
      memset((void*)0x2000009e, 0, 13);
      *(uint8_t*)0x200000ab = 0xbb;
      *(uint64_t*)0x20002848 = 0x2c;
      *(uint64_t*)0x20000358 = 1;
      *(uint64_t*)0x20000360 = 0;
      *(uint64_t*)0x20000368 = 0;
      *(uint32_t*)0x20000370 = 0;
      syscall(__NR_sendmsg, /*fd=*/r[0], /*msg=*/0x20000340ul, /*f=*/0ul);
      break;
    case 4:
      res = syscall(__NR_socket, /*domain=*/0xaul, /*type=*/6ul, /*proto=*/0);
      if (res != -1) r[3] = res;
      break;
    case 5:
      *(uint16_t*)0x20000000 = 0xa;
      *(uint16_t*)0x20000002 = htobe16(0);
      *(uint32_t*)0x20000004 = htobe32(0);
      *(uint64_t*)0x20000008 = htobe64(0);
      *(uint64_t*)0x20000010 = htobe64(0xa0211fffe000000);
      *(uint32_t*)0x20000018 = 0;
      syscall(__NR_connect, /*fd=*/r[3], /*addr=*/0x20000000ul,
              /*addrlen=*/0x1cul);
      break;
    case 6:
      res = syscall(__NR_dup, /*oldfd=*/r[3]);
      if (res != -1) r[4] = res;
      break;
    case 7:
      *(uint64_t*)0x20000200 = 0;
      *(uint32_t*)0x20000208 = 0;
      *(uint64_t*)0x20000210 = 0;
      *(uint64_t*)0x20000218 = 0;
      *(uint64_t*)0x20000220 = 0;
      *(uint64_t*)0x20000228 = 0;
      *(uint32_t*)0x20000230 = 0;
      *(uint32_t*)0x20000238 = 0;
      syscall(__NR_sendmmsg, /*fd=*/r[4], /*mmsg=*/0x20000200ul, /*vlen=*/1ul,
              /*f=*/0x48000ul);
      break;
    case 8:
      syscall(__NR_shutdown, /*fd=*/r[3], /*how=*/0ul);
      break;
    case 9:
      *(uint16_t*)0x20000000 = 0xa;
      *(uint16_t*)0x20000002 = htobe16(0);
      *(uint32_t*)0x20000004 = htobe32(0);
      *(uint64_t*)0x20000008 = htobe64(0);
      *(uint64_t*)0x20000010 = htobe64(0xa0211fffe000000);
      *(uint32_t*)0x20000018 = 0;
      syscall(__NR_connect, /*fd=*/r[3], /*addr=*/0x20000000ul,
              /*addrlen=*/0x1cul);
      break;
  }
}
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);
  loop();
  return 0;
}

repro.txt

r0 = socket(0x10, 0x803, 0x0)
r1 = socket$inet6(0xa, 0x1, 0x0)
ioctl$ifreq_SIOCGIFINDEX_wireguard(r1, 0x8933, &(0x7f00000001c0)={'wg1\x00', <r2=>0x0})
sendmsg$nl_route(r0, &(0x7f0000000340)={0x0, 0x0, &(0x7f0000002840)={&(0x7f0000000080)=@ipv6_newaddr={0x2c, 0x14, 0x1, 0x0, 0x0, {0xa, 0x0, 0x0, 0x0, r2}, [@IFA_LOCAL={0x14, 0x2, @remote}]}, 0x2c}}, 0x0)
r3 = socket$inet6(0xa, 0x6, 0x0)
connect$inet6(r3, &(0x7f0000000000)={0xa, 0x0, 0x0, @loopback={0x0, 0xa0211fffe000000}}, 0x1c)
r4 = dup(r3)
sendmmsg$inet6(r4, &(0x7f0000000200)=[{{0x0, 0x0, 0x0}}], 0x1, 0x48000)
shutdown(r3, 0x0)
connect$inet6(r3, &(0x7f0000000000)={0xa, 0x0, 0x0, @loopback={0x0, 0xa0211fffe000000}}, 0x1c)