[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 19.809759] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. [ 20.971475] random: sshd: uninitialized urandom read (32 bytes read) Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 21.241403] random: sshd: uninitialized urandom read (32 bytes read) [ 21.815315] random: sshd: uninitialized urandom read (32 bytes read) [ 21.993611] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.15.211' (ECDSA) to the list of known hosts. [ 27.615498] random: sshd: uninitialized urandom read (32 bytes read) executing program [ 27.714138] [ 27.715815] ====================================================== [ 27.722110] WARNING: possible circular locking dependency detected [ 27.728403] 4.19.0-rc2+ #3 Not tainted [ 27.732264] ------------------------------------------------------ [ 27.738575] syz-executor840/4287 is trying to acquire lock: [ 27.744264] 00000000f2b9c463 (&sb->s_type->i_mutex_key#10){++++}, at: shmem_fallocate+0x18b/0x12e0 [ 27.753355] [ 27.753355] but task is already holding lock: [ 27.759305] 00000000fae7365c (ashmem_mutex){+.+.}, at: ashmem_shrink_scan+0xb4/0x630 [ 27.767181] [ 27.767181] which lock already depends on the new lock. [ 27.767181] [ 27.775493] [ 27.775493] the existing dependency chain (in reverse order) is: [ 27.783092] [ 27.783092] -> #2 (ashmem_mutex){+.+.}: [ 27.788538] __mutex_lock+0x171/0x1700 [ 27.792927] mutex_lock_nested+0x16/0x20 [ 27.797495] ashmem_mmap+0x55/0x520 [ 27.801625] mmap_region+0xf27/0x1c50 [ 27.805928] do_mmap+0xa10/0x1220 [ 27.809885] vm_mmap_pgoff+0x213/0x2c0 [ 27.814273] ksys_mmap_pgoff+0x4da/0x660 [ 27.818852] __x64_sys_mmap+0xe9/0x1b0 [ 27.823417] do_syscall_64+0x1b9/0x820 [ 27.827820] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 27.833519] [ 27.833519] -> #1 (&mm->mmap_sem){++++}: [ 27.839084] __might_fault+0x155/0x1e0 [ 27.843476] _copy_to_user+0x30/0x110 [ 27.847782] filldir+0x1ea/0x3a0 [ 27.851651] dcache_readdir+0x13a/0x620 [ 27.856126] iterate_dir+0x48b/0x5d0 [ 27.860344] __x64_sys_getdents+0x29f/0x510 [ 27.865167] do_syscall_64+0x1b9/0x820 [ 27.869566] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 27.875255] [ 27.875255] -> #0 (&sb->s_type->i_mutex_key#10){++++}: [ 27.882002] lock_acquire+0x1e4/0x4f0 [ 27.886319] down_write+0x8f/0x130 [ 27.890361] shmem_fallocate+0x18b/0x12e0 [ 27.895048] ashmem_shrink_scan+0x236/0x630 [ 27.899872] ashmem_ioctl+0x3ae/0x13a0 [ 27.904266] do_vfs_ioctl+0x1de/0x1720 [ 27.908656] ksys_ioctl+0xa9/0xd0 [ 27.912609] __x64_sys_ioctl+0x73/0xb0 [ 27.917000] do_syscall_64+0x1b9/0x820 [ 27.921392] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 27.927078] [ 27.927078] other info that might help us debug this: [ 27.927078] [ 27.935202] Chain exists of: [ 27.935202] &sb->s_type->i_mutex_key#10 --> &mm->mmap_sem --> ashmem_mutex [ 27.935202] [ 27.946766] Possible unsafe locking scenario: [ 27.946766] [ 27.952804] CPU0 CPU1 [ 27.957447] ---- ---- [ 27.962102] lock(ashmem_mutex); [ 27.965531] lock(&mm->mmap_sem); [ 27.971567] lock(ashmem_mutex); [ 27.977515] lock(&sb->s_type->i_mutex_key#10); [ 27.982252] [ 27.982252] *** DEADLOCK *** [ 27.982252] [ 27.988292] 1 lock held by syz-executor840/4287: [ 27.993024] #0: 00000000fae7365c (ashmem_mutex){+.+.}, at: ashmem_shrink_scan+0xb4/0x630 [ 28.001334] [ 28.001334] stack backtrace: [ 28.005812] CPU: 0 PID: 4287 Comm: syz-executor840 Not tainted 4.19.0-rc2+ #3 [ 28.013060] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 28.022391] Call Trace: [ 28.024963] dump_stack+0x1c9/0x2b4 [ 28.028573] ? dump_stack_print_info.cold.2+0x52/0x52 [ 28.033748] ? vprintk_func+0x81/0x117 [ 28.037619] print_circular_bug.isra.34.cold.55+0x1bd/0x27d [ 28.043310] ? save_trace+0xe0/0x290 [ 28.047007] __lock_acquire+0x3449/0x5020 [ 28.051138] ? lock_pin_lock+0x350/0x350 [ 28.055180] ? mark_held_locks+0x160/0x160 [ 28.059408] ? mark_held_locks+0x160/0x160 [ 28.063623] ? __bfs+0xb0/0x7b0 [ 28.066881] ? __bfs+0xb0/0x7b0 [ 28.070144] ? graph_lock+0x170/0x170 [ 28.073942] ? print_usage_bug+0xc0/0xc0 [ 28.077987] ? pagevec_lru_move_fn+0x1ad/0x270 [ 28.082552] ? trace_hardirqs_off_caller+0x2b0/0x2b0 [ 28.087637] ? graph_lock+0x170/0x170 [ 28.091418] ? graph_lock+0x170/0x170 [ 28.095216] lock_acquire+0x1e4/0x4f0 [ 28.099241] ? shmem_fallocate+0x18b/0x12e0 [ 28.103549] ? lock_release+0x9f0/0x9f0 [ 28.107506] ? check_same_owner+0x340/0x340 [ 28.111808] ? mark_held_locks+0x160/0x160 [ 28.116024] ? rcu_note_context_switch+0x680/0x680 [ 28.120937] down_write+0x8f/0x130 [ 28.124460] ? shmem_fallocate+0x18b/0x12e0 [ 28.128763] ? down_read+0x1d0/0x1d0 [ 28.132458] ? kasan_check_write+0x14/0x20 [ 28.136675] ? do_raw_spin_lock+0xc1/0x200 [ 28.140891] shmem_fallocate+0x18b/0x12e0 [ 28.145023] ? depot_save_stack+0x291/0x470 [ 28.149346] ? save_stack+0xa9/0xd0 [ 28.152954] ? save_stack+0x43/0xd0 [ 28.156566] ? shmem_setattr+0xda0/0xda0 [ 28.160619] ? ashmem_ioctl+0x1181/0x13a0 [ 28.164749] ? do_vfs_ioctl+0x1de/0x1720 [ 28.168789] ? ksys_ioctl+0xa9/0xd0 [ 28.172399] ? __x64_sys_ioctl+0x73/0xb0 [ 28.176444] ? do_syscall_64+0x1b9/0x820 [ 28.180486] ? entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 28.185833] ? find_held_lock+0x36/0x1c0 [ 28.189876] ? find_held_lock+0x36/0x1c0 [ 28.193919] ? lock_acquire+0x1e4/0x4f0 [ 28.197876] ? ashmem_shrink_scan+0xb4/0x630 [ 28.202269] ? lock_downgrade+0x8f0/0x8f0 [ 28.206412] ? lock_release+0x9f0/0x9f0 [ 28.210367] ? __lock_is_held+0xb5/0x140 [ 28.214413] ? mutex_trylock+0x24c/0x2b0 [ 28.218455] ? ashmem_shrink_scan+0xb4/0x630 [ 28.222844] ? __mutex_add_waiter+0x2a0/0x2a0 [ 28.227319] ? wait_for_completion+0x8d0/0x8d0 [ 28.231887] ashmem_shrink_scan+0x236/0x630 [ 28.236199] ? cap_capable+0x1f9/0x260 [ 28.240082] ? ashmem_release+0x190/0x190 [ 28.244233] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 28.249758] ? ns_capable_common+0x13f/0x170 [ 28.254149] ashmem_ioctl+0x3ae/0x13a0 [ 28.258020] ? smk_access_entry+0x300/0x300 [ 28.262328] ? ashmem_shrink_scan+0x630/0x630 [ 28.266803] ? smk_tskacc+0x3dd/0x520 [ 28.270585] ? find_held_lock+0x36/0x1c0 [ 28.274626] ? smack_privileged+0xd0/0xd0 [ 28.278757] ? ashmem_shrink_scan+0x630/0x630 [ 28.283249] do_vfs_ioctl+0x1de/0x1720 [ 28.287123] ? ioctl_preallocate+0x300/0x300 [ 28.291512] ? memset+0x31/0x40 [ 28.294795] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 28.300316] ? smack_file_ioctl+0x210/0x3c0 [ 28.304620] ? fget_raw+0x20/0x20 [ 28.308052] ? smack_file_lock+0x2e0/0x2e0 [ 28.312273] ? do_syscall_64+0x9a/0x820 [ 28.316242] ? do_syscall_64+0x9a/0x820 [ 28.320227] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 28.325758] ? security_file_ioctl+0x94/0xc0 [ 28.330151] ksys_ioctl+0xa9/0xd0 [ 28.333589] __x64_sys_ioctl+0x73/0xb0 [ 28.337461] do_syscall_64+0x1b9/0x820 [ 28.341330] ? entry_SYSCALL_64_after_hwframe+0x3e/0xbe [ 28.346674] ? syscall_return_slowpath+0x5e0/0x5e0 [ 28.351587] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 28.356415] ? trace_hardirqs_on_caller+0x2c0/0x2c0 [ 28.361420] ? prepare_exit_to_usermode+0x291/0x3b0 [ 28.366418] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 28.371252] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 28.376423] RIP: 0033:0x440089 [ 28.379598] 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 [ 28.398482] RSP: 002b:00007ffd5d6f9eb8 EFLAGS: 00000217 ORIG_RAX: 0000000000000010 [ 28.406193] RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440089 [ 28.413464] RDX: 0000000000000000 RSI: 00000