Date:   Mon, 12 Feb 2018 07:54:49 -0800
From:   syzbot <syzbot+421677102422908e104e@...kaller.appspotmail.com>
To:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com, viro@...iv.linux.org.uk
Subject: KASAN: use-after-free Read in do_raw_spin_unlock (2)

Hello,

syzbot hit the following crash on upstream commit
f1517df8701c9f12dae9ce7f43a5d300a6917619 (Thu Feb 8 23:18:32 2018 +0000)
Merge tag 'nfsd-4.16' of git://linux-nfs.org/~bfields/linux

C reproducer is attached.
syzkaller reproducer is attached.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

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Reported-by: syzbot+421677102422908e104e@...kaller.appspotmail.com
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==================================================================
BUG: KASAN: use-after-free in debug_spin_unlock  
kernel/locking/spinlock_debug.c:100 [inline]
BUG: KASAN: use-after-free in do_raw_spin_unlock+0x2a4/0x300  
kernel/locking/spinlock_debug.c:134
Read of size 4 at addr ffff8801af8d1328 by task syzkaller254122/4773

CPU: 0 PID: 4773 Comm: syzkaller254122 Not tainted 4.15.0+ #305
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 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:256
  kasan_report_error mm/kasan/report.c:354 [inline]
  kasan_report+0x23b/0x360 mm/kasan/report.c:412
  __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
  debug_spin_unlock kernel/locking/spinlock_debug.c:100 [inline]
  do_raw_spin_unlock+0x2a4/0x300 kernel/locking/spinlock_debug.c:134
  __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:159 [inline]
  _raw_spin_unlock_irqrestore+0x27/0xba kernel/locking/spinlock.c:184
  spin_unlock_irqrestore include/linux/spinlock.h:365 [inline]
  remove_wait_queue+0x1b4/0x350 kernel/sched/wait.c:52
  ep_remove_wait_queue fs/eventpoll.c:595 [inline]
  ep_unregister_pollwait.isra.7+0x18c/0x590 fs/eventpoll.c:613
  ep_free+0x13f/0x320 fs/eventpoll.c:830
  ep_eventpoll_release+0x44/0x60 fs/eventpoll.c:862
  __fput+0x327/0x7e0 fs/file_table.c:209
  ____fput+0x15/0x20 fs/file_table.c:243
  task_work_run+0x199/0x270 kernel/task_work.c:113
  tracehook_notify_resume include/linux/tracehook.h:191 [inline]
  exit_to_usermode_loop+0x275/0x2f0 arch/x86/entry/common.c:166
  prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
  syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
  do_syscall_64+0x6ed/0x940 arch/x86/entry/common.c:292
  entry_SYSCALL_64_after_hwframe+0x26/0x9b
RIP: 0033:0x44a0f9
RSP: 002b:00007f03daef9da8 EFLAGS: 00000246 ORIG_RAX: 0000000000000124
RAX: 0000000000000008 RBX: 00000000006debfc RCX: 000000000044a0f9
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000007
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006debf8
R13: 6e69622f7665642f R14: 6273752f7665642f R15: 000000000000000b

Allocated by task 4761:
  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:552
  kmem_cache_alloc_trace+0x136/0x740 mm/slab.c:3607
  kmalloc include/linux/slab.h:512 [inline]
  kzalloc include/linux/slab.h:701 [inline]
  binder_get_thread+0x1cf/0x870 drivers/android/binder.c:4279
  binder_poll+0x8c/0x390 drivers/android/binder.c:4393
  ep_item_poll.isra.10+0xf2/0x320 fs/eventpoll.c:885
  ep_insert+0x6a2/0x1ac0 fs/eventpoll.c:1457
  SYSC_epoll_ctl fs/eventpoll.c:2104 [inline]
  SyS_epoll_ctl+0x12bf/0x1a80 fs/eventpoll.c:1990
  do_syscall_64+0x282/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x26/0x9b

Freed by task 4761:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
  set_track mm/kasan/kasan.c:459 [inline]
  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
  __cache_free mm/slab.c:3485 [inline]
  kfree+0xd9/0x260 mm/slab.c:3800
  binder_free_thread drivers/android/binder.c:4306 [inline]
  binder_thread_dec_tmpref+0x27f/0x310 drivers/android/binder.c:1879
  binder_thread_release+0x4a1/0x6b0 drivers/android/binder.c:4382
  binder_ioctl+0xc02/0x1417 drivers/android/binder.c:4599
  vfs_ioctl fs/ioctl.c:46 [inline]
  do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
  SYSC_ioctl fs/ioctl.c:701 [inline]
  SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
  do_syscall_64+0x282/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x26/0x9b

The buggy address belongs to the object at ffff8801af8d1280
  which belongs to the cache kmalloc-512 of size 512
The buggy address is located 168 bytes inside of
  512-byte region [ffff8801af8d1280, ffff8801af8d1480)
The buggy address belongs to the page:
page:ffffea0006be3440 count:1 mapcount:0 mapping:ffff8801af8d1000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801af8d1000 0000000000000000 0000000100000006
raw: ffffea0006bcd4a0 ffffea0006bb3e60 ffff8801db000940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801af8d1200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801af8d1280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8801af8d1300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                   ^
  ffff8801af8d1380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801af8d1400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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