[   38.051541] audit: type=1800 audit(1549181200.653:27): pid=7567 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="restorecond" dev="sda1" ino=2436 res=0
[   38.077325] audit: type=1800 audit(1549181200.653:28): pid=7567 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="ssh" dev="sda1" ino=2417 res=0
[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c.
[....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c.
[   38.917253] audit: type=1800 audit(1549181201.573:29): pid=7567 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="rc.local" dev="sda1" ino=2432 res=0
[   38.936094] audit: type=1800 audit(1549181201.573:30): pid=7567 uid=0 auid=4294967295 ses=4294967295 subj=_ 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 '10.128.0.168' (ECDSA) to the list of known hosts.
executing program
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syzkaller login: [   47.145342] 
[   47.147023] ======================================================
[   47.153333] WARNING: possible circular locking dependency detected
[   47.159649] 5.0.0-rc4+ #58 Not tainted
[   47.163520] ------------------------------------------------------
[   47.169823] syz-executor490/7725 is trying to acquire lock:
[   47.175528] 000000005d06bb3b (&mm->mmap_sem){++++}, at: __do_page_fault+0x9c2/0xd60
[   47.183332] 
[   47.183332] but task is already holding lock:
[   47.189286] 00000000e7af72fa (&sb->s_type->i_mutex_key#11){+.+.}, at: generic_file_write_iter+0xdf/0x610
[   47.198903] 
[   47.198903] which lock already depends on the new lock.
[   47.198903] 
[   47.207202] 
[   47.207202] the existing dependency chain (in reverse order) is:
[   47.214804] 
[   47.214804] -> #2 (&sb->s_type->i_mutex_key#11){+.+.}:
[   47.221591]        down_write+0x38/0x90
[   47.225576]        shmem_fallocate+0x15a/0xc60
[   47.230162]        ashmem_shrink_scan+0x1d7/0x4f0
[   47.234993]        ashmem_ioctl+0x2f0/0x11a0
[   47.239390]        do_vfs_ioctl+0xd6e/0x1390
[   47.243786]        ksys_ioctl+0xab/0xd0
[   47.247755]        __x64_sys_ioctl+0x73/0xb0
[   47.252168]        do_syscall_64+0x103/0x610
[   47.256569]        entry_SYSCALL_64_after_hwframe+0x49/0xbe
[   47.262262] 
[   47.262262] -> #1 (ashmem_mutex){+.+.}:
[   47.267708]        __mutex_lock+0xf7/0x1310
[   47.272029]        mutex_lock_nested+0x16/0x20
[   47.276621]        ashmem_mmap+0x55/0x520
[   47.280760]        mmap_region+0xc37/0x1760
[   47.285068]        do_mmap+0x8e2/0x1080
[   47.289032]        vm_mmap_pgoff+0x1c5/0x230
[   47.293431]        ksys_mmap_pgoff+0x4aa/0x630
[   47.297999]        __x64_sys_mmap+0xe9/0x1b0
[   47.302397]        do_syscall_64+0x103/0x610
[   47.306794]        entry_SYSCALL_64_after_hwframe+0x49/0xbe
[   47.312485] 
[   47.312485] -> #0 (&mm->mmap_sem){++++}:
[   47.318017]        lock_acquire+0x16f/0x3f0
[   47.322328]        down_read+0x3b/0x90
[   47.326205]        __do_page_fault+0x9c2/0xd60
[   47.330777]        do_page_fault+0x71/0x581
[   47.335088]        page_fault+0x1e/0x30
[   47.339053]        iov_iter_fault_in_readable+0x377/0x450
[   47.344578]        generic_perform_write+0x195/0x530
[   47.349692]        __generic_file_write_iter+0x25e/0x630
[   47.355181]        generic_file_write_iter+0x360/0x610
[   47.360449]        __vfs_write+0x613/0x8e0
[   47.364671]        vfs_write+0x20c/0x580
[   47.368718]        ksys_write+0xea/0x1f0
[   47.372770]        __x64_sys_write+0x73/0xb0
[   47.377172]        do_syscall_64+0x103/0x610
[   47.381569]        entry_SYSCALL_64_after_hwframe+0x49/0xbe
[   47.387259] 
[   47.387259] other info that might help us debug this:
[   47.387259] 
[   47.395381] Chain exists of:
[   47.395381]   &mm->mmap_sem --> ashmem_mutex --> &sb->s_type->i_mutex_key#11
[   47.395381] 
[   47.406900]  Possible unsafe locking scenario:
[   47.406900] 
[   47.412940]        CPU0                    CPU1
[   47.417649]        ----                    ----
[   47.422303]   lock(&sb->s_type->i_mutex_key#11);
[   47.427059]                                lock(ashmem_mutex);
[   47.433018]                                lock(&sb->s_type->i_mutex_key#11);
[   47.440279]   lock(&mm->mmap_sem);
[   47.443848] 
[   47.443848]  *** DEADLOCK ***
[   47.443848] 
[   47.449899] 2 locks held by syz-executor490/7725:
[   47.454723]  #0: 00000000e1b23a2e (sb_writers#5){.+.+}, at: vfs_write+0x429/0x580
[   47.462344]  #1: 00000000e7af72fa (&sb->s_type->i_mutex_key#11){+.+.}, at: generic_file_write_iter+0xdf/0x610
[   47.472396] 
[   47.472396] stack backtrace:
[   47.476900] CPU: 0 PID: 7725 Comm: syz-executor490 Not tainted 5.0.0-rc4+ #58
[   47.484169] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[   47.493509] Call Trace:
[   47.496101]  dump_stack+0x172/0x1f0
[   47.499720]  print_circular_bug.isra.0.cold+0x1cc/0x28f
[   47.505072]  __lock_acquire+0x2f00/0x4700
[   47.509220]  ? mark_held_locks+0x100/0x100
[   47.513453]  ? mark_held_locks+0x100/0x100
[   47.517677]  ? __lock_is_held+0xb6/0x140
[   47.521728]  lock_acquire+0x16f/0x3f0
[   47.525521]  ? __do_page_fault+0x9c2/0xd60
[   47.529755]  down_read+0x3b/0x90
[   47.533112]  ? __do_page_fault+0x9c2/0xd60
[   47.537338]  __do_page_fault+0x9c2/0xd60
[   47.541395]  do_page_fault+0x71/0x581
[   47.545183]  page_fault+0x1e/0x30
[   47.548638] RIP: 0010:iov_iter_fault_in_readable+0x377/0x450
[   47.554425] 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
[   47.573313] RSP: 0018:ffff888091e079b8 EFLAGS: 00010293
[   47.578664] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000020e1ec3f
[   47.585923] RDX: 0000000000000000 RSI: ffffffff8328b1e7 RDI: 0000000000000007
[   47.593182] RBP: ffff888091e07a58 R08: ffff8880a8ed6140 R09: fffff9400041a407
[   47.600472] R10: fffff9400041a406 R11: ffffea00020d2037 R12: 0000000000001000
[   47.607819] R13: 0000000000001000 R14: 0000000000000000 R15: ffff888091e07a30
[   47.615120]  ? iov_iter_fault_in_readable+0x367/0x450
[   47.620312]  ? iov_iter_fault_in_readable+0x367/0x450
[   47.625489]  ? copy_page_from_iter+0x750/0x750
[   47.630061]  generic_perform_write+0x195/0x530
[   47.634644]  ? page_endio+0x780/0x780
[   47.638435]  ? current_time+0x140/0x140
[   47.642402]  ? lock_acquire+0x16f/0x3f0
[   47.646415]  __generic_file_write_iter+0x25e/0x630
[   47.651335]  ? __sanitizer_cov_trace_cmp8+0x18/0x20
[   47.656343]  generic_file_write_iter+0x360/0x610
[   47.661091]  ? __generic_file_write_iter+0x630/0x630
[   47.666183]  ? __fget+0x340/0x540
[   47.669642]  ? __sanitizer_cov_trace_const_cmp8+0x18/0x20
[   47.675168]  ? iov_iter_init+0xea/0x220
[   47.679134]  __vfs_write+0x613/0x8e0
[   47.682898]  ? kernel_read+0x120/0x120
[   47.686790]  ? rcu_read_lock_sched_held+0x110/0x130
[   47.691807]  ? rcu_sync_lockdep_assert+0x73/0xb0
[   47.696551]  ? __sanitizer_cov_trace_const_cmp4+0x16/0x20
[   47.702078]  ? __sb_start_write+0x1ac/0x360
[   47.706390]  vfs_write+0x20c/0x580
[   47.709921]  ksys_write+0xea/0x1f0
[   47.713452]  ? __ia32_sys_read+0xb0/0xb0
[   47.717506]  ? do_syscall_64+0x26/0x610
[   47.721471]  ? entry_SYSCALL_64_after_hwframe+0x49/0xbe
[   47.726872]  ? do_syscall_64+0x26/0x610
[   47.730891]  __x64_sys_write+0x73/0xb0
[   47.734776]  do_syscall_64+0x103/0x610
[   47.738766]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
[   47.743942] RIP: 0033:0x4463e9
[   47.747122] Code: e8 2c b3 02 00 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 2b 09 fc ff c3 66 2e 0f 1f 84 00 00 00 00
[   47.766010] RSP: 002b:00007f57570bfda8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[   47.773715] RAX: ffffffffffffffda RBX: 00000000006dbc28 RCX: 00000000004463e9
[   47.780985] RDX: 00000000fffffe43 RSI: 0000000020000c40 RDI: 0000000000000004
[   47.788279] RBP: 00000000006dbc20 R08: 0000000000000000 R09: 0000000000000000
executing program
[   47.795543] R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc2c
[   47.802812] R13: 0000000000000000 R14: 0080000080000000 R15: 20c49ba5e353f7cf
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