Subject: KASAN: use-after-free Read in worker_thread (2)

From: syzbot <[email-masked]>
Date: Sat, 11 Nov 2017 07:56:01 -0800

syzkaller has found reproducer for the following crash on  
d9e0e63d9a6f88440eb201e1491fcf730272c706
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.

syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers

BUG: KASAN: use-after-free in worker_thread+0x15bb/0x1990  
kernel/workqueue.c:2244
Read of size 8 at addr ffff88002d0e3de0 by task kworker/u8:1/1209

CPU: 0 PID: 1209 Comm: kworker/u8:1 Not tainted 4.14.0-rc8-next-20171110+  
#12
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:17 [inline]
  dump_stack+0x194/0x257 lib/dump_stack.c:53
  print_address_description+0x73/0x250 mm/kasan/report.c:252
  kasan_report_error mm/kasan/report.c:351 [inline]
  kasan_report+0x25b/0x340 mm/kasan/report.c:409
  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
  worker_thread+0x15bb/0x1990 kernel/workqueue.c:2244
  kthread+0x37a/0x440 kernel/kthread.c:238
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:437

Allocated by task 11866:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
  set_track mm/kasan/kasan.c:459 [inline]
  kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
  kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
  kmem_cache_alloc+0x12e/0x760 mm/slab.c:3548
  kmem_cache_zalloc include/linux/slab.h:693 [inline]
  kcm_attach net/kcm/kcmsock.c:1394 [inline]
  kcm_attach_ioctl net/kcm/kcmsock.c:1460 [inline]
  kcm_ioctl+0x2d1/0x1610 net/kcm/kcmsock.c:1695
  sock_do_ioctl+0x65/0xb0 net/socket.c:960
  sock_ioctl+0x2c2/0x440 net/socket.c:1057
  vfs_ioctl fs/ioctl.c:46 [inline]
  do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
  SYSC_ioctl fs/ioctl.c:701 [inline]
  SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
  entry_SYSCALL_64_fastpath+0x1f/0x96

Freed by task 11867:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
  set_track mm/kasan/kasan.c:459 [inline]
  kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
  __cache_free mm/slab.c:3492 [inline]
  kmem_cache_free+0x77/0x280 mm/slab.c:3750
  kcm_unattach+0xe50/0x1510 net/kcm/kcmsock.c:1563
  kcm_unattach_ioctl net/kcm/kcmsock.c:1608 [inline]
  kcm_ioctl+0xdf0/0x1610 net/kcm/kcmsock.c:1705
  sock_do_ioctl+0x65/0xb0 net/socket.c:960
  sock_ioctl+0x2c2/0x440 net/socket.c:1057
  vfs_ioctl fs/ioctl.c:46 [inline]
  do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
  SYSC_ioctl fs/ioctl.c:701 [inline]
  SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
  entry_SYSCALL_64_fastpath+0x1f/0x96

The buggy address belongs to the object at ffff88002d0e3d00
  which belongs to the cache kcm_psock_cache of size 576
The buggy address is located 224 bytes inside of
  576-byte region [ffff88002d0e3d00, ffff88002d0e3f40)
The buggy address belongs to the page:
page:ffffea0000b43880 count:1 mapcount:0 mapping:ffff88002d0e2180 index:0x0  
compound_mapcount: 0
flags: 0x100000000008100(slab|head)
raw: 0100000000008100 ffff88002d0e2180 0000000000000000 000000010000000b
raw: ffffea0000b14920 ffffea0000b27e20 ffff88002b0089c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff88002d0e3c80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff88002d0e3d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88002d0e3d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                        ^
  ffff88002d0e3e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff88002d0e3e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================