[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 23.795944] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. [ 24.348657] random: sshd: uninitialized urandom read (32 bytes read) [ 24.718115] random: sshd: uninitialized urandom read (32 bytes read) Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 25.295986] random: sshd: uninitialized urandom read (32 bytes read) [ 25.471409] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.0' (ECDSA) to the list of known hosts. [ 31.121064] random: sshd: uninitialized urandom read (32 bytes read) executing program [ 31.220877] [ 31.222537] ====================================================== [ 31.228834] WARNING: possible circular locking dependency detected [ 31.235150] 4.18.0-next-20180817+ #42 Not tainted [ 31.239967] ------------------------------------------------------ [ 31.246264] syz-executor610/4474 is trying to acquire lock: [ 31.251955] 000000004f4029f2 (&sb->s_type->i_mutex_key#10){++++}, at: shmem_fallocate+0x18b/0x12e0 [ 31.261063] [ 31.261063] but task is already holding lock: [ 31.267015] 0000000094d6a464 (ashmem_mutex){+.+.}, at: ashmem_shrink_scan+0xb4/0x630 [ 31.274893] [ 31.274893] which lock already depends on the new lock. [ 31.274893] [ 31.283212] [ 31.283212] the existing dependency chain (in reverse order) is: [ 31.290811] [ 31.290811] -> #2 (ashmem_mutex){+.+.}: [ 31.296262] __mutex_lock+0x171/0x1700 [ 31.300655] mutex_lock_nested+0x16/0x20 [ 31.305245] ashmem_mmap+0x55/0x520 [ 31.309401] mmap_region+0xf27/0x1c50 [ 31.313706] do_mmap+0xa10/0x1220 [ 31.317666] vm_mmap_pgoff+0x213/0x2c0 [ 31.322056] ksys_mmap_pgoff+0x4da/0x660 [ 31.326623] __x64_sys_mmap+0xe9/0x1b0 [ 31.331022] do_syscall_64+0x1b9/0x820 [ 31.335414] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 31.341099] [ 31.341099] -> #1 (&mm->mmap_sem){++++}: [ 31.346630] __might_fault+0x155/0x1e0 [ 31.351022] _copy_to_user+0x30/0x110 [ 31.355326] filldir+0x1ea/0x3a0 [ 31.359199] dcache_readdir+0x13a/0x620 [ 31.363676] iterate_dir+0x48b/0x5d0 [ 31.367890] __x64_sys_getdents+0x29f/0x510 [ 31.372717] do_syscall_64+0x1b9/0x820 [ 31.377110] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 31.382800] [ 31.382800] -> #0 (&sb->s_type->i_mutex_key#10){++++}: [ 31.389551] lock_acquire+0x1e4/0x4f0 [ 31.393863] down_write+0x8f/0x130 [ 31.397909] shmem_fallocate+0x18b/0x12e0 [ 31.402559] ashmem_shrink_scan+0x236/0x630 [ 31.407382] ashmem_ioctl+0x3ae/0x13a0 [ 31.411792] do_vfs_ioctl+0x1de/0x1720 [ 31.416183] ksys_ioctl+0xa9/0xd0 [ 31.420138] __x64_sys_ioctl+0x73/0xb0 [ 31.424528] do_syscall_64+0x1b9/0x820 [ 31.428923] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 31.434608] [ 31.434608] other info that might help us debug this: [ 31.434608] [ 31.442728] Chain exists of: [ 31.442728] &sb->s_type->i_mutex_key#10 --> &mm->mmap_sem --> ashmem_mutex [ 31.442728] [ 31.454255] Possible unsafe locking scenario: [ 31.454255] [ 31.460300] CPU0 CPU1 [ 31.464942] ---- ---- [ 31.469671] lock(ashmem_mutex); [ 31.473113] lock(&mm->mmap_sem); [ 31.479149] lock(ashmem_mutex); [ 31.485097] lock(&sb->s_type->i_mutex_key#10); [ 31.489833] [ 31.489833] *** DEADLOCK *** [ 31.489833] [ 31.495896] 1 lock held by syz-executor610/4474: [ 31.500626] #0: 0000000094d6a464 (ashmem_mutex){+.+.}, at: ashmem_shrink_scan+0xb4/0x630 [ 31.508945] [ 31.508945] stack backtrace: [ 31.513446] CPU: 0 PID: 4474 Comm: syz-executor610 Not tainted 4.18.0-next-20180817+ #42 [ 31.521653] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 31.530987] Call Trace: [ 31.533562] dump_stack+0x1c9/0x2b4 [ 31.537172] ? dump_stack_print_info.cold.2+0x52/0x52 [ 31.542353] ? vprintk_func+0x81/0x117 [ 31.546226] print_circular_bug.isra.34.cold.55+0x1bd/0x27d [ 31.552030] ? save_trace+0xe0/0x290 [ 31.555725] __lock_acquire+0x3449/0x5020 [ 31.559857] ? lock_pin_lock+0x350/0x350 [ 31.563904] ? mark_held_locks+0x160/0x160 [ 31.568122] ? mark_held_locks+0x160/0x160 [ 31.572339] ? __bfs+0xb0/0x7b0 [ 31.575599] ? __bfs+0xb0/0x7b0 [ 31.578865] ? graph_lock+0x170/0x170 [ 31.582648] ? print_usage_bug+0xc0/0xc0 [ 31.586693] ? pagevec_lru_move_fn+0x1ad/0x270 [ 31.591258] ? trace_hardirqs_off_caller+0x2b0/0x2b0 [ 31.596351] ? graph_lock+0x170/0x170 [ 31.600135] ? graph_lock+0x170/0x170 [ 31.603919] lock_acquire+0x1e4/0x4f0 [ 31.607713] ? shmem_fallocate+0x18b/0x12e0 [ 31.612019] ? lock_release+0x9f0/0x9f0 [ 31.615978] ? check_same_owner+0x340/0x340 [ 31.620293] ? mark_held_locks+0x160/0x160 [ 31.624515] ? rcu_note_context_switch+0x680/0x680 [ 31.629432] down_write+0x8f/0x130 [ 31.632958] ? shmem_fallocate+0x18b/0x12e0 [ 31.637277] ? down_read+0x1d0/0x1d0 [ 31.640986] ? kasan_check_write+0x14/0x20 [ 31.645209] ? do_raw_spin_lock+0xc1/0x200 [ 31.649431] shmem_fallocate+0x18b/0x12e0 [ 31.653569] ? depot_save_stack+0x291/0x470 [ 31.657879] ? save_stack+0xa9/0xd0 [ 31.661491] ? save_stack+0x43/0xd0 [ 31.665103] ? shmem_setattr+0xda0/0xda0 [ 31.669151] ? ashmem_ioctl+0x1181/0x13a0 [ 31.673290] ? do_vfs_ioctl+0x1de/0x1720 [ 31.677337] ? ksys_ioctl+0xa9/0xd0 [ 31.680945] ? __x64_sys_ioctl+0x73/0xb0 [ 31.684993] ? do_syscall_64+0x1b9/0x820 [ 31.689039] ? entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 31.694391] ? find_held_lock+0x36/0x1c0 [ 31.698440] ? find_held_lock+0x36/0x1c0 [ 31.702489] ? lock_acquire+0x1e4/0x4f0 [ 31.706451] ? ashmem_shrink_scan+0xb4/0x630 [ 31.710845] ? lock_downgrade+0x8f0/0x8f0 [ 31.715000] ? lock_release+0x9f0/0x9f0 [ 31.718957] ? __lock_is_held+0xb5/0x140 [ 31.723003] ? mutex_trylock+0x24c/0x2b0 [ 31.727047] ? ashmem_shrink_scan+0xb4/0x630 [ 31.731440] ? __mutex_add_waiter+0x2a0/0x2a0 [ 31.735918] ? wait_for_completion+0x8d0/0x8d0 [ 31.740488] ashmem_shrink_scan+0x236/0x630 [ 31.744806] ? cap_capable+0x1f9/0x260 [ 31.748714] ? ashmem_release+0x190/0x190 [ 31.752881] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 31.758403] ? ns_capable_common+0x13f/0x170 [ 31.762799] ashmem_ioctl+0x3ae/0x13a0 [ 31.766673] ? ashmem_shrink_scan+0x630/0x630 [ 31.771187] ? find_held_lock+0x36/0x1c0 [ 31.775239] ? __do_page_fault+0x620/0xe50 [ 31.779464] ? ashmem_shrink_scan+0x630/0x630 [ 31.783947] do_vfs_ioctl+0x1de/0x1720 [ 31.787824] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x20 [ 31.793344] ? ioctl_preallocate+0x300/0x300 [ 31.797738] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 31.803261] ? __fget_light+0x2f7/0x440 [ 31.807224] ? __handle_mm_fault+0x4370/0x4370 [ 31.811794] ? fget_raw+0x20/0x20 [ 31.815242] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 31.820775] ? __do_page_fault+0x449/0xe50 [ 31.825018] ? do_syscall_64+0x9a/0x820 [ 31.828974] ? do_syscall_64+0x9a/0x820 [ 31.832932] ? lockdep_hardirqs_on+0x421/0x5c0 [ 31.837498] ? security_file_ioctl+0x94/0xc0 [ 31.841891] ksys_ioctl+0xa9/0xd0 [ 31.845331] __x64_sys_ioctl+0x73/0xb0 [ 31.849202] do_syscall_64+0x1b9/0x820 [ 31.853074] ? entry_SYSCALL_64_after_hwframe+0x3e/0xbe [ 31.858419] ? syscall_return_slowpath+0x5e0/0x5e0 [ 31.863336] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 31.868163] ? trace_hardirqs_on_caller+0x2b0/0x2b0 [ 31.873159] ? prepare_exit_to_usermode+0x291/0x3b0 [ 31.878160] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 31.882988] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 31.888160] RIP: 0033:0x440099 [ 31.891338] 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 [ 31.910219] RSP: 002b:00007fff0474b5b8 EFLAGS: 00000217 ORIG_RAX: 0000000000000010 [ 31.917907] RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000