[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 21.534621] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. [ 22.453614] random: sshd: uninitialized urandom read (32 bytes read) [ 22.709199] random: sshd: uninitialized urandom read (32 bytes read) Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 23.249295] random: sshd: uninitialized urandom read (32 bytes read) [ 23.422499] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.17' (ECDSA) to the list of known hosts. [ 29.050393] random: sshd: uninitialized urandom read (32 bytes read) executing program [ 29.152146] [ 29.153877] ====================================================== [ 29.160245] WARNING: possible circular locking dependency detected [ 29.166553] 4.18.0-rc8-next-20180810+ #36 Not tainted [ 29.171738] ------------------------------------------------------ [ 29.178043] syz-executor495/4427 is trying to acquire lock: [ 29.183788] 00000000ea653b20 (&sb->s_type->i_mutex_key#9){++++}, at: shmem_fallocate+0x18b/0x12e0 [ 29.192852] [ 29.192852] but task is already holding lock: [ 29.198813] 00000000579f5759 (ashmem_mutex){+.+.}, at: ashmem_shrink_scan+0xb4/0x630 [ 29.206697] [ 29.206697] which lock already depends on the new lock. [ 29.206697] [ 29.215001] [ 29.215001] the existing dependency chain (in reverse order) is: [ 29.222611] [ 29.222611] -> #2 (ashmem_mutex){+.+.}: [ 29.228078] __mutex_lock+0x171/0x1700 [ 29.232481] mutex_lock_nested+0x16/0x20 [ 29.237055] ashmem_mmap+0x55/0x520 [ 29.241194] mmap_region+0xf27/0x1c50 [ 29.245530] do_mmap+0xa10/0x1220 [ 29.249495] vm_mmap_pgoff+0x213/0x2c0 [ 29.253893] ksys_mmap_pgoff+0x4da/0x660 [ 29.258473] __x64_sys_mmap+0xe9/0x1b0 [ 29.262873] do_syscall_64+0x1b9/0x820 [ 29.267273] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 29.272974] [ 29.272974] -> #1 (&mm->mmap_sem){++++}: [ 29.278563] __might_fault+0x155/0x1e0 [ 29.283064] _copy_to_user+0x30/0x110 [ 29.287378] filldir+0x1ea/0x3a0 [ 29.291260] dcache_readdir+0x13a/0x620 [ 29.295748] iterate_dir+0x48b/0x5d0 [ 29.299977] __x64_sys_getdents+0x29f/0x510 [ 29.304812] do_syscall_64+0x1b9/0x820 [ 29.309265] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 29.314961] [ 29.314961] -> #0 (&sb->s_type->i_mutex_key#9){++++}: [ 29.321645] lock_acquire+0x1e4/0x540 [ 29.325972] down_write+0x8f/0x130 [ 29.330027] shmem_fallocate+0x18b/0x12e0 [ 29.334692] ashmem_shrink_scan+0x236/0x630 [ 29.339835] ashmem_ioctl+0x3ae/0x13a0 [ 29.344252] do_vfs_ioctl+0x1de/0x1720 [ 29.348663] ksys_ioctl+0xa9/0xd0 [ 29.352635] __x64_sys_ioctl+0x73/0xb0 [ 29.357040] do_syscall_64+0x1b9/0x820 [ 29.361438] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 29.367132] [ 29.367132] other info that might help us debug this: [ 29.367132] [ 29.375264] Chain exists of: [ 29.375264] &sb->s_type->i_mutex_key#9 --> &mm->mmap_sem --> ashmem_mutex [ 29.375264] [ 29.386708] Possible unsafe locking scenario: [ 29.386708] [ 29.392753] CPU0 CPU1 [ 29.397405] ---- ---- [ 29.402059] lock(ashmem_mutex); [ 29.405499] lock(&mm->mmap_sem); [ 29.411543] lock(ashmem_mutex); [ 29.417510] lock(&sb->s_type->i_mutex_key#9); [ 29.422170] [ 29.422170] *** DEADLOCK *** [ 29.422170] [ 29.428238] 1 lock held by syz-executor495/4427: [ 29.432982] #0: 00000000579f5759 (ashmem_mutex){+.+.}, at: ashmem_shrink_scan+0xb4/0x630 [ 29.441302] [ 29.441302] stack backtrace: [ 29.445790] CPU: 1 PID: 4427 Comm: syz-executor495 Not tainted 4.18.0-rc8-next-20180810+ #36 [ 29.454352] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 29.463694] Call Trace: [ 29.466324] dump_stack+0x1c9/0x2b4 [ 29.469943] ? dump_stack_print_info.cold.2+0x52/0x52 [ 29.475130] ? vprintk_func+0x81/0x117 [ 29.479013] print_circular_bug.isra.37.cold.58+0x1bd/0x27d [ 29.484716] ? save_trace+0xe0/0x290 [ 29.488419] __lock_acquire+0x3449/0x5020 [ 29.492567] ? lock_pin_lock+0x350/0x350 [ 29.496650] ? trace_hardirqs_on+0x10/0x10 [ 29.500877] ? trace_hardirqs_on+0x10/0x10 [ 29.505103] ? __bfs+0xb0/0x7b0 [ 29.508374] ? __bfs+0xb0/0x7b0 [ 29.511653] ? graph_lock+0x170/0x170 [ 29.515442] ? print_usage_bug+0xc0/0xc0 [ 29.519495] ? graph_lock+0x170/0x170 [ 29.523289] ? graph_lock+0x170/0x170 [ 29.527083] ? find_held_lock+0x36/0x1c0 [ 29.531136] lock_acquire+0x1e4/0x540 [ 29.534982] ? shmem_fallocate+0x18b/0x12e0 [ 29.539297] ? lock_release+0xa30/0xa30 [ 29.543310] ? check_same_owner+0x340/0x340 [ 29.547633] ? trace_hardirqs_on+0x10/0x10 [ 29.551863] ? rcu_note_context_switch+0x730/0x730 [ 29.556787] down_write+0x8f/0x130 [ 29.560321] ? shmem_fallocate+0x18b/0x12e0 [ 29.564642] ? down_read+0x1d0/0x1d0 [ 29.568350] ? _raw_spin_unlock_irqrestore+0x74/0xc0 [ 29.573445] ? trace_hardirqs_on_caller+0x421/0x5c0 [ 29.578452] shmem_fallocate+0x18b/0x12e0 [ 29.582607] ? depot_save_stack+0x291/0x470 [ 29.586986] ? save_stack+0xa9/0xd0 [ 29.590616] ? save_stack+0x43/0xd0 [ 29.594253] ? shmem_setattr+0xda0/0xda0 [ 29.598312] ? ashmem_ioctl+0x1181/0x13a0 [ 29.602454] ? do_vfs_ioctl+0x1de/0x1720 [ 29.606510] ? ksys_ioctl+0xa9/0xd0 [ 29.610128] ? __x64_sys_ioctl+0x73/0xb0 [ 29.614181] ? do_syscall_64+0x1b9/0x820 [ 29.618253] ? entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 29.623621] ? find_held_lock+0x36/0x1c0 [ 29.627682] ? find_held_lock+0x36/0x1c0 [ 29.631734] ? lock_acquire+0x1e4/0x540 [ 29.635702] ? ashmem_shrink_scan+0xb4/0x630 [ 29.640099] ? lock_downgrade+0x8f0/0x8f0 [ 29.644253] ? kasan_check_read+0x11/0x20 [ 29.648454] ? lock_release+0xa30/0xa30 [ 29.652427] ? __lock_is_held+0xb5/0x140 [ 29.656485] ? mutex_trylock+0x24c/0x2b0 [ 29.660537] ? ashmem_shrink_scan+0xb4/0x630 [ 29.664938] ? __mutex_add_waiter+0x2a0/0x2a0 [ 29.669424] ? wait_for_completion+0x8d0/0x8d0 [ 29.674001] ashmem_shrink_scan+0x236/0x630 [ 29.678316] ? cap_capable+0x1f9/0x260 [ 29.682194] ? ashmem_release+0x190/0x190 [ 29.686359] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 29.691888] ? ns_capable_common+0x13f/0x170 [ 29.696289] ashmem_ioctl+0x3ae/0x13a0 [ 29.700172] ? ashmem_shrink_scan+0x630/0x630 [ 29.704702] ? find_held_lock+0x36/0x1c0 [ 29.708757] ? ashmem_shrink_scan+0x630/0x630 [ 29.713257] do_vfs_ioctl+0x1de/0x1720 [ 29.717137] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x20 [ 29.722668] ? ioctl_preallocate+0x300/0x300 [ 29.727068] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 29.732605] ? __fget_light+0x2f7/0x440 [ 29.736590] ? __handle_mm_fault+0x4470/0x4470 [ 29.741176] ? fget_raw+0x20/0x20 [ 29.744636] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 29.750169] ? __do_page_fault+0x449/0xe50 [ 29.754397] ? mm_fault_error+0x380/0x380 [ 29.758539] ? security_file_ioctl+0x94/0xc0 [ 29.762948] ksys_ioctl+0xa9/0xd0 [ 29.766400] __x64_sys_ioctl+0x73/0xb0 [ 29.770284] do_syscall_64+0x1b9/0x820 [ 29.774163] ? syscall_slow_exit_work+0x500/0x500 [ 29.779049] ? syscall_return_slowpath+0x5e0/0x5e0 [ 29.783978] ? syscall_return_slowpath+0x31d/0x5e0 [ 29.788901] ? entry_SYSCALL_64_after_hwframe+0x59/0xbe [ 29.794259] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 29.799093] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 29.804273] RIP: 0033:0x4400c9 [ 29.807461] Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00 [ 29.826362] RSP: 002b:00007ffde889ba68 EFLAGS: 00000217 ORIG_RAX: 0000000000000010 [ 29.834118] RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004400c9 [ 29.841379] RDX: 0000000000000000 RSI: 000000000000770a RDI: 0000000000000003 [ 29.848645] RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000000000