[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c.
[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c.
[....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c.
[   34.809580] kauditd_printk_skb: 8 callbacks suppressed
[   34.809591] audit: type=1800 audit(1550799664.683:29): pid=7375 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="rc.local" dev="sda1" ino=2432 res=0
[   34.841340] audit: type=1800 audit(1550799664.683:30): pid=7375 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="rmnologin" dev="sda1" ino=2423 res=0

Debian GNU/Linux 7 syzkaller ttyS0

Warning: Permanently added '10.128.10.39' (ECDSA) to the list of known hosts.
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syzkaller login: [  103.170976] hrtimer: interrupt took 28278 ns
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[  104.222022] 
[  104.223686] ======================================================
[  104.230134] WARNING: possible circular locking dependency detected
[  104.236450] 5.0.0-rc7+ #83 Not tainted
[  104.240325] ------------------------------------------------------
[  104.246632] syz-executor024/7591 is trying to acquire lock:
[  104.252329] 000000003fe6d951 (&mm->mmap_sem){++++}, at: __do_page_fault+0x9c2/0xd60
[  104.260132] 
[  104.260132] but task is already holding lock:
[  104.266100] 000000006e381745 (&sb->s_type->i_mutex_key#12){+.+.}, at: generic_file_write_iter+0xdf/0x610
[  104.275734] 
[  104.275734] which lock already depends on the new lock.
[  104.275734] 
[  104.284386] 
[  104.284386] the existing dependency chain (in reverse order) is:
[  104.292004] 
[  104.292004] -> #2 (&sb->s_type->i_mutex_key#12){+.+.}:
[  104.298762]        down_write+0x38/0x90
[  104.302741]        shmem_fallocate+0x15a/0xc60
[  104.307326]        ashmem_shrink_scan+0x1d7/0x4f0
[  104.312179]        ashmem_ioctl+0x2f0/0x11a0
[  104.316585]        do_vfs_ioctl+0xd6e/0x1390
[  104.321004]        ksys_ioctl+0xab/0xd0
[  104.324981]        __x64_sys_ioctl+0x73/0xb0
[  104.329389]        do_syscall_64+0x103/0x610
[  104.333799]        entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  104.339497] 
[  104.339497] -> #1 (ashmem_mutex){+.+.}:
[  104.344957]        __mutex_lock+0xf7/0x1310
[  104.349279]        mutex_lock_nested+0x16/0x20
[  104.353863]        ashmem_mmap+0x55/0x520
[  104.358009]        mmap_region+0xc37/0x1760
[  104.362327]        do_mmap+0x8e2/0x1080
[  104.366300]        vm_mmap_pgoff+0x1c5/0x230
[  104.370711]        ksys_mmap_pgoff+0x4aa/0x630
[  104.375289]        __x64_sys_mmap+0xe9/0x1b0
[  104.379705]        do_syscall_64+0x103/0x610
[  104.384116]        entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  104.389829] 
[  104.389829] -> #0 (&mm->mmap_sem){++++}:
[  104.395372]        lock_acquire+0x16f/0x3f0
[  104.399690]        down_read+0x3b/0x90
[  104.403574]        __do_page_fault+0x9c2/0xd60
[  104.408153]        do_page_fault+0x71/0x581
[  104.412476]        page_fault+0x1e/0x30
[  104.416451]        iov_iter_fault_in_readable+0x377/0x450
[  104.421993]        generic_perform_write+0x195/0x530
[  104.427105]        __generic_file_write_iter+0x25e/0x630
[  104.432558]        generic_file_write_iter+0x360/0x610
[  104.437839]        __vfs_write+0x613/0x8e0
[  104.442157]        vfs_write+0x20c/0x580
[  104.446226]        ksys_write+0xea/0x1f0
[  104.450281]        __x64_sys_write+0x73/0xb0
[  104.454676]        do_syscall_64+0x103/0x610
[  104.459093]        entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  104.464782] 
[  104.464782] other info that might help us debug this:
[  104.464782] 
[  104.472901] Chain exists of:
[  104.472901]   &mm->mmap_sem --> ashmem_mutex --> &sb->s_type->i_mutex_key#12
[  104.472901] 
[  104.484430]  Possible unsafe locking scenario:
[  104.484430] 
[  104.490470]        CPU0                    CPU1
[  104.495130]        ----                    ----
[  104.499775]   lock(&sb->s_type->i_mutex_key#12);
[  104.504512]                                lock(ashmem_mutex);
[  104.510462]                                lock(&sb->s_type->i_mutex_key#12);
[  104.517718]   lock(&mm->mmap_sem);
[  104.521412] 
[  104.521412]  *** DEADLOCK ***
[  104.521412] 
[  104.527466] 2 locks held by syz-executor024/7591:
[  104.532292]  #0: 00000000a76030fb (sb_writers#5){.+.+}, at: vfs_write+0x429/0x580
[  104.539914]  #1: 000000006e381745 (&sb->s_type->i_mutex_key#12){+.+.}, at: generic_file_write_iter+0xdf/0x610
[  104.549971] 
[  104.549971] stack backtrace:
[  104.554454] CPU: 1 PID: 7591 Comm: syz-executor024 Not tainted 5.0.0-rc7+ #83
[  104.561709] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[  104.571052] Call Trace:
[  104.573626]  dump_stack+0x172/0x1f0
[  104.577237]  print_circular_bug.isra.0.cold+0x1cc/0x28f
[  104.582601]  __lock_acquire+0x2f00/0x4700
[  104.586750]  ? mark_held_locks+0x100/0x100
[  104.590975]  ? mark_held_locks+0x100/0x100
[  104.595196]  ? __lock_is_held+0xb6/0x140
[  104.599265]  lock_acquire+0x16f/0x3f0
[  104.603055]  ? __do_page_fault+0x9c2/0xd60
[  104.607276]  down_read+0x3b/0x90
[  104.610640]  ? __do_page_fault+0x9c2/0xd60
[  104.614861]  __do_page_fault+0x9c2/0xd60
[  104.618906]  do_page_fault+0x71/0x581
[  104.622694]  page_fault+0x1e/0x30
[  104.626137] RIP: 0010:iov_iter_fault_in_readable+0x377/0x450
[  104.631922] Code: 89 f6 41 88 57 e0 e8 b8 2b 47 fe 45 85 f6 74 c1 e9 70 fe ff ff e8 29 2a 47 fe 0f 1f 00 0f ae e8 44 89 f0 48 8b 8d 68 ff ff ff <8a> 11 89 c3 0f 1f 00 41 88 57 d0 31 ff 89 de e8 85 2b 47 fe 85 db
[  104.651071] RSP: 0018:ffff88808f7df9b8 EFLAGS: 00010293
[  104.656415] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000020e0b53f
[  104.663668] RDX: 0000000000000000 RSI: ffffffff8328b757 RDI: 0000000000000007
[  104.670920] RBP: ffff88808f7dfa58 R08: ffff88809aca0700 R09: fffff94000454e6f
[  104.678176] R10: fffff94000454e6e R11: ffffea00022a7377 R12: 0000000000001000
[  104.685539] R13: 0000000000001000 R14: 0000000000000000 R15: ffff88808f7dfa30
[  104.692797]  ? iov_iter_fault_in_readable+0x367/0x450
[  104.697972]  ? iov_iter_fault_in_readable+0x367/0x450
[  104.703142]  ? copy_page_from_iter+0x750/0x750
[  104.707708]  generic_perform_write+0x195/0x530
[  104.712278]  ? page_endio+0x780/0x780
[  104.716065]  ? current_time+0x140/0x140
[  104.720044]  ? lock_acquire+0x16f/0x3f0
[  104.724005]  __generic_file_write_iter+0x25e/0x630
[  104.728923]  ? __sanitizer_cov_trace_cmp8+0x18/0x20
[  104.733929]  generic_file_write_iter+0x360/0x610
[  104.738671]  ? __generic_file_write_iter+0x630/0x630
[  104.743753]  ? __fget+0x340/0x540
[  104.747190]  ? __sanitizer_cov_trace_const_cmp8+0x18/0x20
[  104.752708]  ? iov_iter_init+0xea/0x220
[  104.756666]  __vfs_write+0x613/0x8e0
[  104.760361]  ? kernel_read+0x120/0x120
[  104.764234]  ? rcu_read_lock_sched_held+0x110/0x130
[  104.769233]  ? rcu_sync_lockdep_assert+0x73/0xb0
[  104.773971]  ? __sanitizer_cov_trace_const_cmp4+0x16/0x20
[  104.779503]  ? __sb_start_write+0x1ac/0x360
[  104.783814]  vfs_write+0x20c/0x580
[  104.787437]  ksys_write+0xea/0x1f0
[  104.790962]  ? __ia32_sys_read+0xb0/0xb0
[  104.795011]  ? do_syscall_64+0x26/0x610
[  104.798980]  ? entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  104.804339]  ? do_syscall_64+0x26/0x610
[  104.808301]  __x64_sys_write+0x73/0xb0
[  104.812177]  do_syscall_64+0x103/0x610
[  104.816049]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
[  104.821373] RIP: 0033:0x446599
[  104.824557] Code: e8 0c e8 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 7b 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00
[  104.843441] RSP: 002b:00007f861e1fbdb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[  104.851144] RAX: ffffffffffffffda RBX: 00000000006dbc28 RCX: 0000000000446599
[  104.858406] RDX: 00000000fffffda2 RSI: 0000000020000540 RDI: 0000000000000005
[  104.865654] RBP: 00000000006dbc20 R08: 0000000000000000 R09: 0000000000000000
[  104.872908] R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc2c
[  104.880159] R13: 00007fff433879df R14: 00007f861e1fc9c0 R15: 0000000000000000
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