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Date:   Wed, 02 Jan 2019 02:31:04 -0800
From:   syzbot <syzbot+239d99847eb49ecb3899@...kaller.appspotmail.com>
To:     bfields@...ldses.org, jlayton@...nel.org,
        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 posix_lock_inode

Hello,

syzbot found the following crash on:

HEAD commit:    e1ef035d272e Merge tag 'armsoc-defconfig' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16bb4c4b400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9c6a26e22579190b
dashboard link: https://syzkaller.appspot.com/bug?extid=239d99847eb49ecb3899
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=128aa377400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+239d99847eb49ecb3899@...kaller.appspotmail.com

IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready
IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready
8021q: adding VLAN 0 to HW filter on device batadv0
8021q: adding VLAN 0 to HW filter on device batadv0
==================================================================
BUG: KASAN: use-after-free in what_owner_is_waiting_for fs/locks.c:1000  
[inline]
BUG: KASAN: use-after-free in posix_locks_deadlock fs/locks.c:1023 [inline]
BUG: KASAN: use-after-free in posix_lock_inode+0x1f9e/0x2750 fs/locks.c:1163
Read of size 8 at addr ffff88808791b000 by task syz-executor2/10100

CPU: 1 PID: 10100 Comm: syz-executor2 Not tainted 4.20.0+ #3
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+0x1db/0x2d0 lib/dump_stack.c:113
  print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
  kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
  __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
  what_owner_is_waiting_for fs/locks.c:1000 [inline]
  posix_locks_deadlock fs/locks.c:1023 [inline]
  posix_lock_inode+0x1f9e/0x2750 fs/locks.c:1163
  posix_lock_file fs/locks.c:1346 [inline]
  vfs_lock_file fs/locks.c:2314 [inline]
  vfs_lock_file+0xc7/0xf0 fs/locks.c:2309
  do_lock_file_wait.part.0+0xe5/0x260 fs/locks.c:2328
  do_lock_file_wait fs/locks.c:2324 [inline]
  fcntl_setlk+0x2f1/0xfe0 fs/locks.c:2413
  do_fcntl+0x843/0x12b0 fs/fcntl.c:370
  __do_sys_fcntl fs/fcntl.c:463 [inline]
  __se_sys_fcntl fs/fcntl.c:448 [inline]
  __x64_sys_fcntl+0x16d/0x1e0 fs/fcntl.c:448
  do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457ec9
Code: 6d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f58bbb50c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000048
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457ec9
RDX: 0000000020000140 RSI: 0000000000000007 RDI: 0000000000000003
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f58bbb516d4
R13: 00000000004be5f0 R14: 00000000004ceab0 R15: 00000000ffffffff

Allocated by task 10100:
  save_stack+0x45/0xd0 mm/kasan/common.c:73
  set_track mm/kasan/common.c:85 [inline]
  kasan_kmalloc mm/kasan/common.c:482 [inline]
  kasan_kmalloc+0xcf/0xe0 mm/kasan/common.c:455
  kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:397
  kmem_cache_alloc+0x12d/0x710 mm/slab.c:3541
  kmem_cache_zalloc include/linux/slab.h:730 [inline]
  locks_alloc_lock+0x8e/0x2f0 fs/locks.c:344
  fcntl_setlk+0xa9/0xfe0 fs/locks.c:2362
  do_fcntl+0x843/0x12b0 fs/fcntl.c:370
  __do_sys_fcntl fs/fcntl.c:463 [inline]
  __se_sys_fcntl fs/fcntl.c:448 [inline]
  __x64_sys_fcntl+0x16d/0x1e0 fs/fcntl.c:448
  do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 10100:
  save_stack+0x45/0xd0 mm/kasan/common.c:73
  set_track mm/kasan/common.c:85 [inline]
  __kasan_slab_free+0x102/0x150 mm/kasan/common.c:444
  kasan_slab_free+0xe/0x10 mm/kasan/common.c:452
  __cache_free mm/slab.c:3485 [inline]
  kmem_cache_free+0x86/0x260 mm/slab.c:3747
  locks_free_lock+0x27a/0x3f0 fs/locks.c:381
  fcntl_setlk+0x7b5/0xfe0 fs/locks.c:2439
  do_fcntl+0x843/0x12b0 fs/fcntl.c:370
  __do_sys_fcntl fs/fcntl.c:463 [inline]
  __se_sys_fcntl fs/fcntl.c:448 [inline]
  __x64_sys_fcntl+0x16d/0x1e0 fs/fcntl.c:448
  do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88808791b000
  which belongs to the cache file_lock_cache of size 264
The buggy address is located 0 bytes inside of
  264-byte region [ffff88808791b000, ffff88808791b108)
The buggy address belongs to the page:
page:ffffea00021e46c0 count:1 mapcount:0 mapping:ffff8880aa16a1c0 index:0x0
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea0002333508 ffffea00021d76c8 ffff8880aa16a1c0
raw: 0000000000000000 ffff88808791b000 000000010000000c 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff88808791af00: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc
  ffff88808791af80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff88808791b000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                    ^
  ffff88808791b080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff88808791b100: fb fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@...glegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with  
syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

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