[....] Starting OpenBSD Secure Shell server: sshd[ 11.643036] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 30.038351] random: sshd: uninitialized urandom read (32 bytes read) [ 30.361031] audit: type=1400 audit(1539729980.847:6): avc: denied { map } for pid=1766 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 [ 30.410384] random: sshd: uninitialized urandom read (32 bytes read) [ 30.892731] random: sshd: uninitialized urandom read (32 bytes read) [ 32.391787] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.84' (ECDSA) to the list of known hosts. [ 38.017137] random: sshd: uninitialized urandom read (32 bytes read) executing program [ 38.129807] audit: type=1400 audit(1539729988.607:7): avc: denied { map } for pid=1784 comm="syz-executor747" path="/root/syz-executor747118084" dev="sda1" ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1 [ 38.134034] [ 38.134036] ====================================================== [ 38.134038] WARNING: possible circular locking dependency detected [ 38.134042] 4.14.76+ #19 Not tainted [ 38.134044] ------------------------------------------------------ [ 38.134047] syz-executor747/1784 is trying to acquire lock: [ 38.134049] (&pipe->mutex/1){+.+.}, at: [] fifo_open+0x156/0x9d0 [ 38.134065] [ 38.134065] but task is already holding lock: [ 38.134066] (&sig->cred_guard_mutex){+.+.}, at: [] prepare_bprm_creds+0x4e/0x110 [ 38.134080] [ 38.134080] which lock already depends on the new lock. [ 38.134080] [ 38.134081] [ 38.134081] the existing dependency chain (in reverse order) is: [ 38.134083] [ 38.134083] -> #1 (&sig->cred_guard_mutex){+.+.}: [ 38.134097] __mutex_lock+0xf5/0x1480 [ 38.134105] proc_pid_attr_write+0x16b/0x280 [ 38.134110] __vfs_write+0xf4/0x5c0 [ 38.134114] __kernel_write+0xf3/0x330 [ 38.134121] write_pipe_buf+0x192/0x250 [ 38.134126] __splice_from_pipe+0x324/0x740 [ 38.134131] splice_from_pipe+0xcf/0x130 [ 38.134136] default_file_splice_write+0x37/0x80 [ 38.134141] SyS_splice+0xd06/0x12a0 [ 38.134147] do_syscall_64+0x19b/0x4b0 [ 38.134152] entry_SYSCALL_64_after_hwframe+0x42/0xb7 [ 38.134154] [ 38.134154] -> #0 (&pipe->mutex/1){+.+.}: [ 38.134166] lock_acquire+0x10f/0x380 [ 38.134172] __mutex_lock+0xf5/0x1480 [ 38.134176] fifo_open+0x156/0x9d0 [ 38.134183] do_dentry_open+0x426/0xda0 [ 38.134189] vfs_open+0x11c/0x210 [ 38.134194] path_openat+0x4eb/0x23a0 [ 38.134199] do_filp_open+0x197/0x270 [ 38.134205] do_open_execat+0x10d/0x5b0 [ 38.134220] do_execveat_common.isra.14+0x6cb/0x1d60 [ 38.134225] SyS_execve+0x34/0x40 [ 38.134230] do_syscall_64+0x19b/0x4b0 [ 38.134235] entry_SYSCALL_64_after_hwframe+0x42/0xb7 [ 38.134237] [ 38.134237] other info that might help us debug this: [ 38.134237] [ 38.134238] Possible unsafe locking scenario: [ 38.134238] [ 38.134240] CPU0 CPU1 [ 38.134241] ---- ---- [ 38.134242] lock(&sig->cred_guard_mutex); [ 38.134246] lock(&pipe->mutex/1); [ 38.134251] lock(&sig->cred_guard_mutex); [ 38.134255] lock(&pipe->mutex/1); [ 38.134260] [ 38.134260] *** DEADLOCK *** [ 38.134260] [ 38.134263] 1 lock held by syz-executor747/1784: [ 38.134265] #0: (&sig->cred_guard_mutex){+.+.}, at: [] prepare_bprm_creds+0x4e/0x110 [ 38.134277] [ 38.134277] stack backtrace: [ 38.134284] CPU: 0 PID: 1784 Comm: syz-executor747 Not tainted 4.14.76+ #19 [ 38.134286] Call Trace: [ 38.134294] dump_stack+0xb9/0x11b [ 38.134303] print_circular_bug.isra.18.cold.43+0x2d3/0x40c [ 38.134309] ? save_trace+0xd6/0x250 [ 38.134316] __lock_acquire+0x2ff9/0x4320 [ 38.134324] ? check_preemption_disabled+0x34/0x160 [ 38.134335] ? trace_hardirqs_on+0x10/0x10 [ 38.134341] ? trace_hardirqs_on_caller+0x381/0x520 [ 38.134348] ? _raw_spin_unlock_irqrestore+0x41/0x70 [ 38.134357] ? __lock_acquire+0x619/0x4320 [ 38.134363] ? alloc_pipe_info+0x15b/0x370 [ 38.134367] ? fifo_open+0x1ef/0x9d0 [ 38.134373] ? do_dentry_open+0x426/0xda0 [ 38.134379] ? vfs_open+0x11c/0x210 [ 38.134384] ? path_openat+0x4eb/0x23a0 [ 38.134391] lock_acquire+0x10f/0x380 [ 38.134396] ? fifo_open+0x156/0x9d0 [ 38.134403] ? fifo_open+0x156/0x9d0 [ 38.134409] __mutex_lock+0xf5/0x1480 [ 38.134415] ? fifo_open+0x156/0x9d0 [ 38.134420] ? fifo_open+0x156/0x9d0 [ 38.134426] ? dput.part.6+0x3b3/0x710 [ 38.134434] ? __ww_mutex_wakeup_for_backoff+0x240/0x240 [ 38.134442] ? fs_reclaim_acquire+0x10/0x10 [ 38.134450] ? fifo_open+0x284/0x9d0 [ 38.134456] ? lock_downgrade+0x560/0x560 [ 38.134461] ? lock_acquire+0x10f/0x380 [ 38.134466] ? fifo_open+0x243/0x9d0 [ 38.134472] ? debug_mutex_init+0x28/0x53 [ 38.134479] ? fifo_open+0x156/0x9d0 [ 38.134484] fifo_open+0x156/0x9d0 [ 38.134491] do_dentry_open+0x426/0xda0 [ 38.134497] ? pipe_release+0x240/0x240 [ 38.134506] vfs_open+0x11c/0x210 [ 38.134513] path_openat+0x4eb/0x23a0 [ 38.134522] ? path_mountpoint+0x9a0/0x9a0 [ 38.134532] ? kasan_kmalloc.part.1+0xa9/0xd0 [ 38.134539] ? kasan_kmalloc.part.1+0x4f/0xd0 [ 38.134544] ? __kmalloc_track_caller+0x104/0x300 [ 38.134550] ? kmemdup+0x20/0x50 [ 38.134568] ? security_prepare_creds+0x7c/0xb0 [ 38.134576] ? prepare_creds+0x225/0x2a0 [ 38.134582] ? prepare_exec_creds+0xc/0xe0 [ 38.134588] ? prepare_bprm_creds+0x62/0x110 [ 38.134595] ? do_execveat_common.isra.14+0x2cd/0x1d60 [ 38.134600] ? SyS_execve+0x34/0x40 [ 38.134604] ? do_syscall_64+0x19b/0x4b0 [ 38.134613] do_filp_open+0x197/0x270 [ 38.134620] ? may_open_dev+0xd0/0xd0 [ 38.134629] ? trace_hardirqs_on+0x10/0x10 [ 38.134635] ? fs_reclaim_acquire+0x10/0x10 [ 38.134647] ? rcu_read_lock_sched_held+0x102/0x120 [ 38.134655] do_open_execat+0x10d/0x5b0 [ 38.134662] ? setup_arg_pages+0x720/0x720 [ 38.134669] ? do_execveat_common.isra.14+0x68d/0x1d60 [ 38.134675] ? lock_downgrade+0x560/0x560 [ 38.134680] ? lock_acquire+0x10f/0x380 [ 38.134687] ? check_preemption_disabled+0x34/0x160 [ 38.134696] do_execveat_common.isra.14+0x6cb/0x1d60 [ 38.134706] ? prepare_bprm_creds+0x110/0x110 [ 38.134713] ? getname_flags+0x222/0x540 [ 38.134720] SyS_execve+0x34/0x40 [ 38.134725] ? setup_new_exec+0x770/0x770 [ 38.134731] do_syscall_64+0x19b/0x4b0 [ 38.134739] entry_SYSCALL_64_after_hwframe+0x42/0xb7 [ 38.134744] RIP: 0033:0x440119 [ 38.134747] RSP: 002b:00007ffce2808428 EFLAGS: 00000217 ORIG_RAX: 000000000000003b [ 38.134754] RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 0000000000440119 [ 38.134758] RDX: 0000000020000600 RSI: 00000000200003c0 RDI: 0000000020000400 [ 38.134761] RBP: 00000000006ca018 R08: 0000000000000000 R09: 0000000000000000 [ 38.134765] R10: 0000000000000000 R11: 0000000000000217 R12: 00000000004019a0 [ 38.134768] R13: 0000000000401a30 R14: 0000000000000000 R15: 0000000000000000