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

From: syzbot <syzbot+20eb18b1ffc36152b560[email-masked]>
Date: Tue, 30 Jan 2018 01:52:02 -0800

syzbot has found reproducer for the following crash on upstream commit
6304672b7f0a5c010002e63a075160856dc4f88d (Tue Jan 30 03:08:02 2018 +0000)
Merge branch 'x86-pti-for-linus' of  
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

So far this crash happened 172 times on linux-next, mmots, upstream.
C reproducer is attached.
syzkaller reproducer is attached.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by:  
syzbot+20eb18b1ffc36152b560[email-masked]
It will help syzbot understand when the bug is fixed.

==================================================================
BUG: KASAN: use-after-free in perf_trace_lock_acquire+0x5b7/0x980  
include/trace/events/lock.h:13
Read of size 8 at addr ffff8801b48e50b8 by task syzkaller241108/8081

CPU: 1 PID: 8081 Comm: syzkaller241108 Not tainted 4.15.0+ #286
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: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
  perf_trace_lock_acquire+0x5b7/0x980 include/trace/events/lock.h:13
  trace_lock_acquire include/trace/events/lock.h:13 [inline]
  lock_acquire+0x394/0x580 kernel/locking/lockdep.c:3914
  __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
  _raw_spin_lock_irqsave+0x96/0xc0 kernel/locking/spinlock.c:152
  remove_wait_queue+0x81/0x350 kernel/sched/wait.c:50
  vhost_poll_stop drivers/vhost/vhost.c:230 [inline]
  vhost_dev_stop+0x15c/0x2a0 drivers/vhost/vhost.c:566
  vhost_net_release+0x6e/0x190 drivers/vhost/net.c:998
  __fput+0x327/0x7e0 fs/file_table.c:210
  ____fput+0x15/0x20 fs/file_table.c:244
  task_work_run+0x199/0x270 kernel/task_work.c:113
  exit_task_work include/linux/task_work.h:22 [inline]
  do_exit+0x9bb/0x1ad0 kernel/exit.c:865
  do_group_exit+0x149/0x400 kernel/exit.c:968
  get_signal+0x73f/0x16c0 kernel/signal.c:2335
  do_signal+0x90/0x1eb0 arch/x86/kernel/signal.c:809
  exit_to_usermode_loop+0x214/0x310 arch/x86/entry/common.c:158
  prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
  syscall_return_slowpath+0x490/0x550 arch/x86/entry/common.c:264
  entry_SYSCALL_64_fastpath+0x9e/0xa0
RIP: 0033:0x44bff9
RSP: 002b:00007ff890dd4da8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 0000000000700054 RCX: 000000000044bff9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000700054
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000700050
R13: 6f68762f7665642f R14: 00007ff890dd59c0 R15: 0000000000000007

Allocated by task 8054:
  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
  kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3610
  kmalloc include/linux/slab.h:499 [inline]
  eventfd_file_create.part.3+0x96/0x250 fs/eventfd.c:441
  eventfd_file_create fs/eventfd.c:483 [inline]
  SYSC_eventfd2 fs/eventfd.c:468 [inline]
  SyS_eventfd2 fs/eventfd.c:458 [inline]
  SYSC_eventfd fs/eventfd.c:485 [inline]
  SyS_eventfd+0x2c/0x80 fs/eventfd.c:483
  entry_SYSCALL_64_fastpath+0x29/0xa0

Freed by task 8081:
  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:3488 [inline]
  kfree+0xd6/0x260 mm/slab.c:3803
  eventfd_free_ctx fs/eventfd.c:72 [inline]
  eventfd_free fs/eventfd.c:79 [inline]
  kref_put include/linux/kref.h:70 [inline]
  eventfd_ctx_put+0x26/0x30 fs/eventfd.c:104
  eventfd_release+0x52/0x60 fs/eventfd.c:113
  __fput+0x327/0x7e0 fs/file_table.c:210
  ____fput+0x15/0x20 fs/file_table.c:244
  task_work_run+0x199/0x270 kernel/task_work.c:113
  exit_task_work include/linux/task_work.h:22 [inline]
  do_exit+0x9bb/0x1ad0 kernel/exit.c:865
  do_group_exit+0x149/0x400 kernel/exit.c:968
  get_signal+0x73f/0x16c0 kernel/signal.c:2335
  do_signal+0x90/0x1eb0 arch/x86/kernel/signal.c:809
  exit_to_usermode_loop+0x214/0x310 arch/x86/entry/common.c:158
  prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
  syscall_return_slowpath+0x490/0x550 arch/x86/entry/common.c:264
  entry_SYSCALL_64_fastpath+0x9e/0xa0

The buggy address belongs to the object at ffff8801b48e5080
  which belongs to the cache kmalloc-96 of size 96
The buggy address is located 56 bytes inside of
  96-byte region [ffff8801b48e5080, ffff8801b48e50e0)
The buggy address belongs to the page:
page:ffffea0006d23940 count:1 mapcount:0 mapping:ffff8801b48e5000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801b48e5000 0000000000000000 0000000100000020
raw: ffffea0006a220e0 ffffea0006cc4320 ffff8801db0004c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801b48e4f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801b48e5000: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
> ffff8801b48e5080: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
                                         ^
  ffff8801b48e5100: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
  ffff8801b48e5180: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
==================================================================