Date:   Tue, 17 Apr 2018 18:02:02 -0700
From:   syzbot <syzbot+c6f45f6af72a45097be2@...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 iput

Hello,

syzbot hit the following crash on upstream commit
a27fc14219f2e3c4a46ba9177b04d9b52c875532 (Mon Apr 16 21:07:39 2018 +0000)
Merge branch 'parisc-4.17-3' of  
git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux
syzbot dashboard link:  
https://syzkaller.appspot.com/bug?extid=c6f45f6af72a45097be2

So far this crash happened 2 times on upstream.
C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5638195895074816
syzkaller reproducer:  
https://syzkaller.appspot.com/x/repro.syz?id=5154296156913664
Raw console output:  
https://syzkaller.appspot.com/x/log.txt?id=5743820952043520
Kernel config:  
https://syzkaller.appspot.com/x/.config?id=-5914490758943236750
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+c6f45f6af72a45097be2@...kaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for  
details.
If you forward the report, please keep this part and the footer.

VFS: Busy inodes after unmount of fuse. Self-destruct in 5 seconds.  Have a  
nice day...
==================================================================
BUG: KASAN: use-after-free in iput_final fs/inode.c:1489 [inline]
BUG: KASAN: use-after-free in iput+0xa05/0xa80 fs/inode.c:1545
Read of size 8 at addr ffff8801d9752770 by task syzkaller802106/4482

CPU: 1 PID: 4482 Comm: syzkaller802106 Not tainted 4.17.0-rc1+ #6
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x1b9/0x294 lib/dump_stack.c:113
  print_address_description+0x6c/0x20b mm/kasan/report.c:256
  kasan_report_error mm/kasan/report.c:354 [inline]
  kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
  iput_final fs/inode.c:1489 [inline]
  iput+0xa05/0xa80 fs/inode.c:1545
  free_trace_uprobe+0xe2/0x1f0 kernel/trace/trace_uprobe.c:292
  destroy_local_trace_uprobe+0x63/0x7e kernel/trace/trace_uprobe.c:1395
  perf_uprobe_destroy+0xf2/0x130 kernel/trace/trace_event_perf.c:342
  _free_event+0x3ff/0x1430 kernel/events/core.c:4445
  put_event+0x48/0x60 kernel/events/core.c:4531
  perf_event_release_kernel+0x8bd/0xf90 kernel/events/core.c:4637
  perf_release+0x37/0x50 kernel/events/core.c:4647
  __fput+0x34d/0x890 fs/file_table.c:209
  ____fput+0x15/0x20 fs/file_table.c:243
  task_work_run+0x1e4/0x290 kernel/task_work.c:113
  exit_task_work include/linux/task_work.h:22 [inline]
  do_exit+0x1aee/0x2730 kernel/exit.c:865
  do_group_exit+0x16f/0x430 kernel/exit.c:968
  get_signal+0x886/0x1960 kernel/signal.c:2469
  do_signal+0x98/0x2040 arch/x86/kernel/signal.c:810
  exit_to_usermode_loop+0x28a/0x310 arch/x86/entry/common.c:162
  prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
  syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
  do_syscall_64+0x6ac/0x800 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4457b9
RSP: 002b:00007f98cec58da8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 0000000000000000 RCX: 00000000004457b9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000006dac3c
RBP: 00000000006dac3c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dac38
R13: 0030656c69662f2e R14: 00007f98cec599c0 R15: 0000000000000001

Allocated by task 4481:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
  set_track mm/kasan/kasan.c:460 [inline]
  kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
  kmem_cache_alloc_trace+0x152/0x780 mm/slab.c:3620
  kmalloc include/linux/slab.h:512 [inline]
  kzalloc include/linux/slab.h:701 [inline]
  alloc_super fs/super.c:186 [inline]
  sget_userns+0x1c7/0xf20 fs/super.c:503
  sget+0x10b/0x150 fs/super.c:558
  mount_nodev+0x33/0x110 fs/super.c:1206
  fuse_mount+0x2c/0x40 fs/fuse/inode.c:1192
  mount_fs+0xae/0x328 fs/super.c:1268
  vfs_kern_mount.part.34+0xd4/0x4d0 fs/namespace.c:1037
  vfs_kern_mount fs/namespace.c:1027 [inline]
  do_new_mount fs/namespace.c:2517 [inline]
  do_mount+0x564/0x3070 fs/namespace.c:2847
  ksys_mount+0x12d/0x140 fs/namespace.c:3063
  __do_sys_mount fs/namespace.c:3077 [inline]
  __se_sys_mount fs/namespace.c:3074 [inline]
  __x64_sys_mount+0xbe/0x150 fs/namespace.c:3074
  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 25:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
  set_track mm/kasan/kasan.c:460 [inline]
  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
  __cache_free mm/slab.c:3498 [inline]
  kfree+0xd9/0x260 mm/slab.c:3813
  destroy_super_work+0x40/0x50 fs/super.c:149
  process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145
  worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279
  kthread+0x345/0x410 kernel/kthread.c:238
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

The buggy address belongs to the object at ffff8801d9752740
  which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 48 bytes inside of
  4096-byte region [ffff8801d9752740, ffff8801d9753740)
The buggy address belongs to the page:
page:ffffea000765d480 count:1 mapcount:0 mapping:ffff8801d9752740 index:0x0  
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801d9752740 0000000000000000 0000000100000001
raw: ffffea000765a1a0 ffffea00076665a0 ffff8801dac00dc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801d9752600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801d9752680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8801d9752700: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                                              ^
  ffff8801d9752780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801d9752800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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