[....] Starting file context maintaining daemon: restorecond[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 11.429732] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 41.771318] random: sshd: uninitialized urandom read (32 bytes read) [ 41.957973] audit: type=1400 audit(1540268596.215:6): avc: denied { map } for pid=1779 comm="bash" path="/bin/bash" dev="sda1" ino=1457 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=system_u:object_r:file_t:s0 tclass=file permissive=1 [ 42.000196] random: sshd: uninitialized urandom read (32 bytes read) [ 42.444082] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.27' (ECDSA) to the list of known hosts. [ 48.083958] urandom_read: 1 callbacks suppressed [ 48.083962] random: sshd: uninitialized urandom read (32 bytes read) executing program [ 48.179278] audit: type=1400 audit(1540268602.435:7): avc: denied { map } for pid=1791 comm="syz-executor176" path="/root/syz-executor176701459" dev="sda1" ino=16482 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1 [ 48.183049] [ 48.183051] ====================================================== [ 48.183052] WARNING: possible circular locking dependency detected [ 48.183055] 4.14.78+ #23 Not tainted [ 48.183056] ------------------------------------------------------ [ 48.183058] syz-executor176/1791 is trying to acquire lock: [ 48.183059] (&pipe->mutex/1){+.+.}, at: [] fifo_open+0x156/0x9d0 [ 48.183071] [ 48.183071] but task is already holding lock: [ 48.183072] (&sig->cred_guard_mutex){+.+.}, at: [] prepare_bprm_creds+0x4e/0x110 [ 48.183080] [ 48.183080] which lock already depends on the new lock. [ 48.183080] [ 48.183081] [ 48.183081] the existing dependency chain (in reverse order) is: [ 48.183082] [ 48.183082] -> #1 (&sig->cred_guard_mutex){+.+.}: [ 48.183091] __mutex_lock+0xf5/0x1480 [ 48.183097] proc_pid_attr_write+0x16b/0x280 [ 48.183099] __vfs_write+0xf4/0x5c0 [ 48.183102] __kernel_write+0xf3/0x330 [ 48.183106] write_pipe_buf+0x192/0x250 [ 48.183109] __splice_from_pipe+0x324/0x740 [ 48.183112] splice_from_pipe+0xcf/0x130 [ 48.183116] default_file_splice_write+0x37/0x80 [ 48.183118] SyS_splice+0xd06/0x12a0 [ 48.183122] do_syscall_64+0x19b/0x4b0 [ 48.183126] entry_SYSCALL_64_after_hwframe+0x42/0xb7 [ 48.183127] [ 48.183127] -> #0 (&pipe->mutex/1){+.+.}: [ 48.183134] lock_acquire+0x10f/0x380 [ 48.183137] __mutex_lock+0xf5/0x1480 [ 48.183140] fifo_open+0x156/0x9d0 [ 48.183144] do_dentry_open+0x426/0xda0 [ 48.183147] vfs_open+0x11c/0x210 [ 48.183151] path_openat+0x4eb/0x23a0 [ 48.183154] do_filp_open+0x197/0x270 [ 48.183157] do_open_execat+0x10d/0x5b0 [ 48.183161] do_execveat_common.isra.14+0x6cb/0x1d60 [ 48.183163] SyS_execve+0x34/0x40 [ 48.183166] do_syscall_64+0x19b/0x4b0 [ 48.183169] entry_SYSCALL_64_after_hwframe+0x42/0xb7 [ 48.183170] [ 48.183170] other info that might help us debug this: [ 48.183170] [ 48.183171] Possible unsafe locking scenario: [ 48.183171] [ 48.183171] CPU0 CPU1 [ 48.183172] ---- ---- [ 48.183173] lock(&sig->cred_guard_mutex); [ 48.183175] lock(&pipe->mutex/1); [ 48.183189] lock(&sig->cred_guard_mutex); [ 48.183191] lock(&pipe->mutex/1); [ 48.183194] [ 48.183194] *** DEADLOCK *** [ 48.183194] [ 48.183196] 1 lock held by syz-executor176/1791: [ 48.183197] #0: (&sig->cred_guard_mutex){+.+.}, at: [] prepare_bprm_creds+0x4e/0x110 [ 48.183204] [ 48.183204] stack backtrace: [ 48.183208] CPU: 0 PID: 1791 Comm: syz-executor176 Not tainted 4.14.78+ #23 [ 48.183209] Call Trace: [ 48.183215] dump_stack+0xb9/0x11b [ 48.183220] print_circular_bug.isra.18.cold.43+0x2d3/0x40c [ 48.183224] ? save_trace+0xd6/0x250 [ 48.183228] __lock_acquire+0x2ff9/0x4320 [ 48.183234] ? check_preemption_disabled+0x34/0x160 [ 48.183240] ? trace_hardirqs_on+0x10/0x10 [ 48.183244] ? trace_hardirqs_on_caller+0x381/0x520 [ 48.183247] ? _raw_spin_unlock_irqrestore+0x41/0x70 [ 48.183253] ? __lock_acquire+0x619/0x4320 [ 48.183255] ? alloc_pipe_info+0x15b/0x370 [ 48.183258] ? fifo_open+0x1ef/0x9d0 [ 48.183262] ? do_dentry_open+0x426/0xda0 [ 48.183265] ? vfs_open+0x11c/0x210 [ 48.183268] ? path_openat+0x4eb/0x23a0 [ 48.183272] lock_acquire+0x10f/0x380 [ 48.183275] ? fifo_open+0x156/0x9d0 [ 48.183279] ? fifo_open+0x156/0x9d0 [ 48.183282] __mutex_lock+0xf5/0x1480 [ 48.183285] ? fifo_open+0x156/0x9d0 [ 48.183288] ? fifo_open+0x156/0x9d0 [ 48.183292] ? dput.part.6+0x3b3/0x710 [ 48.183297] ? __ww_mutex_wakeup_for_backoff+0x240/0x240 [ 48.183302] ? fs_reclaim_acquire+0x10/0x10 [ 48.183306] ? fifo_open+0x284/0x9d0 [ 48.183310] ? lock_downgrade+0x560/0x560 [ 48.183313] ? lock_acquire+0x10f/0x380 [ 48.183316] ? fifo_open+0x243/0x9d0 [ 48.183319] ? debug_mutex_init+0x28/0x53 [ 48.183323] ? fifo_open+0x156/0x9d0 [ 48.183325] fifo_open+0x156/0x9d0 [ 48.183330] do_dentry_open+0x426/0xda0 [ 48.183333] ? pipe_release+0x240/0x240 [ 48.183338] vfs_open+0x11c/0x210 [ 48.183342] path_openat+0x4eb/0x23a0 [ 48.183347] ? path_mountpoint+0x9a0/0x9a0 [ 48.183353] ? kasan_kmalloc.part.1+0xa9/0xd0 [ 48.183356] ? kasan_kmalloc.part.1+0x4f/0xd0 [ 48.183360] ? __kmalloc_track_caller+0x104/0x300 [ 48.183365] ? kmemdup+0x20/0x50 [ 48.183369] ? security_prepare_creds+0x7c/0xb0 [ 48.183373] ? prepare_creds+0x225/0x2a0 [ 48.183377] ? prepare_exec_creds+0xc/0xe0 [ 48.183381] ? prepare_bprm_creds+0x62/0x110 [ 48.183385] ? do_execveat_common.isra.14+0x2cd/0x1d60 [ 48.183387] ? SyS_execve+0x34/0x40 [ 48.183390] ? do_syscall_64+0x19b/0x4b0 [ 48.183395] do_filp_open+0x197/0x270 [ 48.183399] ? may_open_dev+0xd0/0xd0 [ 48.183404] ? trace_hardirqs_on+0x10/0x10 [ 48.183407] ? fs_reclaim_acquire+0x10/0x10 [ 48.183415] ? rcu_read_lock_sched_held+0x102/0x120 [ 48.183419] do_open_execat+0x10d/0x5b0 [ 48.183423] ? setup_arg_pages+0x720/0x720 [ 48.183427] ? do_execveat_common.isra.14+0x68d/0x1d60 [ 48.183431] ? lock_downgrade+0x560/0x560 [ 48.183434] ? lock_acquire+0x10f/0x380 [ 48.183438] ? check_preemption_disabled+0x34/0x160 [ 48.183443] do_execveat_common.isra.14+0x6cb/0x1d60 [ 48.183449] ? prepare_bprm_creds+0x110/0x110 [ 48.183453] ? getname_flags+0x222/0x540 [ 48.183456] SyS_execve+0x34/0x40 [ 48.183460] ? setup_new_exec+0x770/0x770 [ 48.183463] do_syscall_64+0x19b/0x4b0 [ 48.183467] entry_SYSCALL_64_after_hwframe+0x42/0xb7 [ 48.183470] RIP: 0033:0x440149 [ 48.183472] RSP: 002b:00007ffc2cbceef8 EFLAGS: 00000217 ORIG_RAX: 000000000000003b [ 48.183476] RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 0000000000440149 [ 48.183478] RDX: 0000000020000580 RSI: 0000000020000240 RDI: 0000000020000000 [ 48.183480] RBP: 00000000006ca018 R08: 0000000000000000 R09: 0000000000000000 [ 48.183482] R10: 0000000000000000 R11: 0000000000000217 R12: 00000000004019d0 [ 48.183484] R13: 0000000000401a60 R14: 0000000000000000 R15: 0000000000000000