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* net/ipv6: null-ptr-deref in inet6_bind
@ 2016-11-02 21:14 Andrey Konovalov
  2016-11-03 15:39 ` Eric Dumazet
  0 siblings, 1 reply; 6+ messages in thread
From: Andrey Konovalov @ 2016-11-02 21:14 UTC (permalink / raw)
  To: David S. Miller, Alexey Kuznetsov, James Morris,
	Hideaki YOSHIFUJI, Patrick McHardy, netdev, LKML
  Cc: Dmitry Vyukov, Alexander Potapenko, Kostya Serebryany,
	Eric Dumazet, syzkaller

[-- Attachment #1: Type: text/plain, Size: 2130 bytes --]

Hi,

I've got the following error report while running the syzkaller fuzzer:

BUG: unable to handle kernel NULL pointer dereference at           (null)
IP: [<          (null)>]           (null)
PGD 66b6f067 [  102.549865] PUD 66c6e067
PMD 0 [  102.549865]
Oops: 0010 [#1] SMP KASAN
Modules linked in:
CPU: 0 PID: 4143 Comm: a.out Not tainted 4.9.0-rc3+ #336
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff880066b1c200 task.stack: ffff880065b58000
RIP: 0010:[<0000000000000000>]  [<          (null)>]           (null)
RSP: 0018:ffff880065b5fbc0  EFLAGS: 00010246
RAX: ffff880066b1c200 RBX: ffff88006873864a RCX: 0000000000000000
RDX: 0000000000000001 RSI: ffff880068738640 RDI: ffff880063bd3200
RBP: ffff880065b5fd20 R08: 1ffff1000c77a713 R09: dffffc0000000000
R10: ffffffff844fc800 R11: 1ffff1000d0e70c9 R12: ffffffff84e7e040
R13: ffff880068738640 R14: ffff880063bd3200 R15: ffffffff86836380
FS:  00007f40b7acf700(0000) GS:ffff88006cc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000006bb28000 CR4: 00000000000006f0
Stack:
 ffffffff83099988 ffffffff8479f7e8 ffffffff81208580 1ffff1000000000c
 0000000041b58ab3 ffffffff8479f7e8 ffffffff81208580 ffffffff812506ed
 0000000000000007 ffff880065b5fc18 ffffffff812506ed ffff880065b5fcd0
Call Trace:
 [<ffffffff832cf4fc>] inet6_bind+0x8ec/0x1020 net/ipv6/af_inet6.c:384
 [<ffffffff82b7033c>] SYSC_bind+0x1ec/0x250 net/socket.c:1367
 [<ffffffff82b72ae4>] SyS_bind+0x24/0x30 net/socket.c:1353
 [<ffffffff83fc0401>] entry_SYSCALL_64_fastpath+0x1f/0xc2
arch/x86/entry/entry_64.S:209
Code:  Bad RIP value.
RIP  [<          (null)>]           (null)
 RSP <ffff880065b5fbc0>
CR2: 0000000000000000
---[ end trace b5ec698ae4926a97 ]---
Kernel panic - not syncing: Fatal exception in interrupt
Kernel Offset: disabled
---[ end Kernel panic - not syncing: Fatal exception in interrupt

On commit 0c183d92b20b5c84ca655b45ef57b3318b83eb9e (Oct 31).

I'm able to reproduce it with the attached program by running it as:
$ gcc -lpthread inet6-bind-poc.c
$ while true; do ./a.out; done

Thanks!

[-- Attachment #2: inet6-bind-poc.c --]
[-- Type: application/octet-stream, Size: 7394 bytes --]

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

#ifndef __NR_socket
#define __NR_socket 41
#endif
#ifndef __NR_bind
#define __NR_bind 49
#endif
#ifndef __NR_syz_open_dev
#define __NR_syz_open_dev 1000002
#endif
#ifndef __NR_syz_open_pts
#define __NR_syz_open_pts 1000003
#endif
#ifndef __NR_syz_test
#define __NR_syz_test 1000001
#endif
#ifndef __NR_mmap
#define __NR_mmap 9
#endif
#ifndef __NR_connect
#define __NR_connect 42
#endif
#ifndef __NR_syz_fuse_mount
#define __NR_syz_fuse_mount 1000004
#endif
#ifndef __NR_syz_fuseblk_mount
#define __NR_syz_fuseblk_mount 1000005
#endif

#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>

#include <errno.h>
#include <error.h>
#include <fcntl.h>
#include <pthread.h>
#include <setjmp.h>
#include <signal.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

__thread int skip_segv;
__thread jmp_buf segv_env;

static void segv_handler(int sig, siginfo_t* info, void* uctx)
{
  if (__atomic_load_n(&skip_segv, __ATOMIC_RELAXED))
    _longjmp(segv_env, 1);
  exit(sig);
}

static void install_segv_handler()
{
  struct sigaction sa;
  memset(&sa, 0, sizeof(sa));
  sa.sa_sigaction = segv_handler;
  sa.sa_flags = SA_NODEFER | SA_SIGINFO;
  sigaction(SIGSEGV, &sa, NULL);
  sigaction(SIGBUS, &sa, NULL);
}

#define NONFAILING(...)                                                \
  {                                                                    \
    __atomic_fetch_add(&skip_segv, 1, __ATOMIC_SEQ_CST);               \
    if (_setjmp(segv_env) == 0) {                                      \
      __VA_ARGS__;                                                     \
    }                                                                  \
    __atomic_fetch_sub(&skip_segv, 1, __ATOMIC_SEQ_CST);               \
  }

static uintptr_t syz_open_dev(uintptr_t a0, uintptr_t a1, uintptr_t 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));
    buf[sizeof(buf) - 1] = 0;
    while ((hash = strchr(buf, '#'))) {
      *hash = '0' + (char)(a1 % 10);
      a1 /= 10;
    }
    return open(buf, a2, 0);
  }
}

static uintptr_t syz_open_pts(uintptr_t a0, uintptr_t a1)
{

  int ptyno = 0;
  if (ioctl(a0, TIOCGPTN, &ptyno))
    return -1;
  char buf[128];
  sprintf(buf, "/dev/pts/%d", ptyno);
  return open(buf, a1, 0);
}

static uintptr_t syz_fuse_mount(uintptr_t a0, uintptr_t a1,
                                uintptr_t a2, uintptr_t a3,
                                uintptr_t a4, uintptr_t a5)
{

  uint64_t target = a0;
  uint64_t mode = a1;
  uint64_t uid = a2;
  uint64_t gid = a3;
  uint64_t maxread = a4;
  uint64_t flags = a5;

  int fd = open("/dev/fuse", O_RDWR);
  if (fd == -1)
    return fd;
  char buf[1024];
  sprintf(buf, "fd=%d,user_id=%ld,group_id=%ld,rootmode=0%o", fd,
          (long)uid, (long)gid, (unsigned)mode & ~3u);
  if (maxread != 0)
    sprintf(buf + strlen(buf), ",max_read=%ld", (long)maxread);
  if (mode & 1)
    strcat(buf, ",default_permissions");
  if (mode & 2)
    strcat(buf, ",allow_other");
  syscall(SYS_mount, "", target, "fuse", flags, buf);

  return fd;
}

static uintptr_t syz_fuseblk_mount(uintptr_t a0, uintptr_t a1,
                                   uintptr_t a2, uintptr_t a3,
                                   uintptr_t a4, uintptr_t a5,
                                   uintptr_t a6, uintptr_t a7)
{

  uint64_t target = a0;
  uint64_t blkdev = a1;
  uint64_t mode = a2;
  uint64_t uid = a3;
  uint64_t gid = a4;
  uint64_t maxread = a5;
  uint64_t blksize = a6;
  uint64_t flags = a7;

  int fd = open("/dev/fuse", O_RDWR);
  if (fd == -1)
    return fd;
  if (syscall(SYS_mknodat, AT_FDCWD, blkdev, S_IFBLK, makedev(7, 199)))
    return fd;
  char buf[256];
  sprintf(buf, "fd=%d,user_id=%ld,group_id=%ld,rootmode=0%o", fd,
          (long)uid, (long)gid, (unsigned)mode & ~3u);
  if (maxread != 0)
    sprintf(buf + strlen(buf), ",max_read=%ld", (long)maxread);
  if (blksize != 0)
    sprintf(buf + strlen(buf), ",blksize=%ld", (long)blksize);
  if (mode & 1)
    strcat(buf, ",default_permissions");
  if (mode & 2)
    strcat(buf, ",allow_other");
  syscall(SYS_mount, blkdev, target, "fuseblk", flags, buf);

  return fd;
}

static uintptr_t execute_syscall(int nr, uintptr_t a0, uintptr_t a1,
                                 uintptr_t a2, uintptr_t a3,
                                 uintptr_t a4, uintptr_t a5,
                                 uintptr_t a6, uintptr_t a7,
                                 uintptr_t a8)
{
  switch (nr) {
  default:
    return syscall(nr, a0, a1, a2, a3, a4, a5);
  case __NR_syz_test:
    return 0;
  case __NR_syz_open_dev:
    return syz_open_dev(a0, a1, a2);
  case __NR_syz_open_pts:
    return syz_open_pts(a0, a1);
  case __NR_syz_fuse_mount:
    return syz_fuse_mount(a0, a1, a2, a3, a4, a5);
  case __NR_syz_fuseblk_mount:
    return syz_fuseblk_mount(a0, a1, a2, a3, a4, a5, a6, a7);
  }
}

long r[21];
void* thr(void* arg)
{
  switch ((long)arg) {
  case 0:
    r[0] =
        execute_syscall(__NR_mmap, 0x20000000ul, 0xb88000ul, 0x3ul,
                        0x32ul, 0xfffffffffffffffful, 0x0ul, 0, 0, 0);
    break;
  case 1:
    r[1] = execute_syscall(__NR_socket, 0xaul, 0x6ul, 0x0ul, 0, 0, 0, 0,
                           0, 0);
    break;
  case 2:
    r[2] =
        execute_syscall(__NR_mmap, 0x20b88000ul, 0x1000ul, 0x3ul,
                        0x32ul, 0xfffffffffffffffful, 0x0ul, 0, 0, 0);
    break;
  case 3:
    NONFAILING(*(uint16_t*)0x20b88000 = (uint16_t)0xa);
    NONFAILING(*(uint16_t*)0x20b88002 = (uint16_t)0x4242);
    NONFAILING(*(uint32_t*)0x20b88004 = (uint32_t)0x1);
    NONFAILING(*(uint32_t*)0x20b88008 = (uint32_t)0xffffffff);
    NONFAILING(*(uint32_t*)0x20b8800c = (uint32_t)0x1);
    NONFAILING(*(uint32_t*)0x20b88010 = (uint32_t)0x5);
    NONFAILING(*(uint32_t*)0x20b88014 = (uint32_t)0x0);
    NONFAILING(*(uint32_t*)0x20b88018 = (uint32_t)0x100000000);
    r[11] = execute_syscall(__NR_bind, r[1], 0x20b88000ul, 0x1cul, 0, 0,
                            0, 0, 0, 0);
    break;
  case 4:
    NONFAILING(*(uint16_t*)0x20000000 = (uint16_t)0xa);
    NONFAILING(*(uint16_t*)0x20000002 = (uint16_t)0x4242);
    NONFAILING(*(uint32_t*)0x20000004 = (uint32_t)0x400);
    NONFAILING(*(uint32_t*)0x20000008 = (uint32_t)0x100000000000000);
    NONFAILING(*(uint32_t*)0x2000000c = (uint32_t)0x100000000);
    NONFAILING(*(uint32_t*)0x20000010 = (uint32_t)0xffffffffffff0000);
    NONFAILING(*(uint32_t*)0x20000014 = (uint32_t)0x0);
    NONFAILING(*(uint32_t*)0x20000018 = (uint32_t)0xffff);
    r[20] = execute_syscall(__NR_connect, r[1], 0x20000000ul, 0x1cul, 0,
                            0, 0, 0, 0, 0);
    break;
  }
  return 0;
}

int main()
{
  long i;
  pthread_t th[10];

  install_segv_handler();
  memset(r, -1, sizeof(r));
  srand(getpid());
  for (i = 0; i < 5; i++) {
    pthread_create(&th[i], 0, thr, (void*)i);
    usleep(10000);
  }
  for (i = 0; i < 5; i++) {
    pthread_create(&th[5 + i], 0, thr, (void*)i);
    if (rand() % 2)
      usleep(rand() % 10000);
  }
  usleep(100000);
  return 0;
}

^ permalink raw reply	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2016-11-03 20:51 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2016-11-02 21:14 net/ipv6: null-ptr-deref in inet6_bind Andrey Konovalov
2016-11-03 15:39 ` Eric Dumazet
2016-11-03 15:49   ` Andrey Konovalov
2016-11-03 15:59   ` [PATCH net] ipv6: dccp: add missing bind_conflict to dccp_ipv6_mapped Eric Dumazet
2016-11-03 16:22     ` Arnaldo Carvalho de Melo
2016-11-03 20:51     ` David Miller

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