Date:   Wed, 28 Feb 2018 08:59:02 -0800
From:   syzbot <syzbot+16363c99d4134717c05b@...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 remove_wait_queue (2)

Hello,

syzbot hit the following crash on upstream commit
f3afe530d644488a074291da04a69a296ab63046 (Tue Feb 27 22:02:39 2018 +0000)
Merge branch 'fixes-v4.16-rc4' of  
git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security

So far this crash happened 3 times on 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+16363c99d4134717c05b@...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.

audit: type=1400 audit(1519800493.311:7): avc:  denied  { map } for   
pid=4238 comm="syzkaller305740" path="/root/syzkaller305740266" dev="sda1"  
ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023  
tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
==================================================================
BUG: KASAN: use-after-free in __lock_acquire+0x3d4d/0x3e00  
kernel/locking/lockdep.c:3310
Read of size 8 at addr ffff8801afa039c0 by task syzkaller305740/4238

CPU: 1 PID: 4238 Comm: syzkaller305740 Not tainted 4.16.0-rc3+ #332
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+0x194/0x24d 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_load8_noabort+0x14/0x20 mm/kasan/report.c:433
  __lock_acquire+0x3d4d/0x3e00 kernel/locking/lockdep.c:3310
  lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920
  __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
  ep_remove_wait_queue fs/eventpoll.c:596 [inline]
  ep_unregister_pollwait.isra.7+0x18c/0x590 fs/eventpoll.c:614
  ep_free+0x13f/0x320 fs/eventpoll.c:832
  ep_eventpoll_release+0x44/0x60 fs/eventpoll.c:864
  __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
  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
  SYSC_exit_group kernel/exit.c:979 [inline]
  SyS_exit_group+0x1d/0x20 kernel/exit.c:977
  do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x43e958
RSP: 002b:00007ffe63a11468 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000043e958
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
RBP: 00000000004be300 R08: 00000000000000e7 R09: ffffffffffffffd0
R10: 00000000004002c8 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000006cc160 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 4238:
  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
  __do_kmalloc_node mm/slab.c:3669 [inline]
  __kmalloc_node+0x47/0x70 mm/slab.c:3676
  kmalloc_node include/linux/slab.h:554 [inline]
  kvmalloc_node+0x99/0xd0 mm/util.c:419
  kvmalloc include/linux/mm.h:541 [inline]
  kvzalloc include/linux/mm.h:549 [inline]
  alloc_netdev_mqs+0x16d/0xfb0 net/core/dev.c:8299
  ppp_create_interface drivers/net/ppp/ppp_generic.c:3018 [inline]
  ppp_unattached_ioctl drivers/net/ppp/ppp_generic.c:866 [inline]
  ppp_ioctl+0x1715/0x2a50 drivers/net/ppp/ppp_generic.c:602
  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+0x281/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 4238:
  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
  kvfree+0x36/0x60 mm/util.c:438
  netdev_freemem+0x4c/0x60 net/core/dev.c:8253
  netdev_release+0x10a/0x160 net/core/net-sysfs.c:1502
  device_release+0x7c/0x210 drivers/base/core.c:814
  kobject_cleanup lib/kobject.c:646 [inline]
  kobject_release lib/kobject.c:675 [inline]
  kref_put include/linux/kref.h:70 [inline]
  kobject_put+0x14c/0x250 lib/kobject.c:692
  put_device+0x20/0x30 drivers/base/core.c:1931
  free_netdev+0x2f5/0x400 net/core/dev.c:8410
  ppp_destroy_interface+0x2bc/0x390 drivers/net/ppp/ppp_generic.c:3100
  ppp_release+0x12b/0x1a0 drivers/net/ppp/ppp_generic.c:415
  ppp_ioctl+0x3b1/0x2a50 drivers/net/ppp/ppp_generic.c:628
  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+0x281/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff8801afa02e40
  which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 2944 bytes inside of
  4096-byte region [ffff8801afa02e40, ffff8801afa03e40)
The buggy address belongs to the page:
page:ffffea0006be8080 count:1 mapcount:0 mapping:ffff8801afa02e40 index:0x0  
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801afa02e40 0000000000000000 0000000100000001
raw: ffffea0006bee220 ffffea0006bee7a0 ffff8801dac00dc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801afa03880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801afa03900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8801afa03980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                            ^
  ffff8801afa03a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801afa03a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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