[....] Starting enhanced syslogd: rsyslogd[ 14.120025] audit: type=1400 audit(1521401875.979:4): avc: denied { syslog } for pid=3568 comm="rsyslogd" capability=34 scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:system_r:kernel_t:s0 tclass=capability2 permissive=1 [?25l[?1c7[ ok 8[?25h[?0c. [....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. Starting mcstransd: [....] Starting file context maintaining daemon: restorecond[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.0.13' (ECDSA) to the list of known hosts. executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program syzkaller login: [ 26.865217] [ 26.866884] ====================================================== [ 26.873172] [ INFO: possible circular locking dependency detected ] [ 26.879556] 4.9.88-gbb52bba #59 Not tainted [ 26.883845] ------------------------------------------------------- [ 26.890226] syzkaller153371/3744 is trying to acquire lock: [ 26.895906] (&mm->mmap_sem){++++++}, at: [] __might_fault+0xe4/0x1d0 [ 26.904375] but task is already holding lock: [ 26.909009] (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 26.917423] which lock already depends on the new lock. [ 26.917423] [ 26.924405] [ 26.924405] the existing dependency chain (in reverse order) is: [ 26.931993] -> #1 (ashmem_mutex){+.+.+.}: [ 26.936812] lock_acquire+0x12e/0x410 [ 26.941116] mutex_lock_nested+0xbb/0x870 [ 26.945757] ashmem_mmap+0x53/0x400 [ 26.949874] mmap_region+0x7dd/0xfd0 [ 26.954086] do_mmap+0x57b/0xbe0 [ 26.957945] vm_mmap_pgoff+0x16b/0x1b0 [ 26.962325] SyS_mmap_pgoff+0x33f/0x560 [ 26.966801] SyS_mmap+0x16/0x20 [ 26.970575] do_syscall_64+0x1a4/0x490 [ 26.974963] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 26.980552] -> #0 (&mm->mmap_sem){++++++}: [ 26.985399] __lock_acquire+0x2bf9/0x3640 [ 26.990036] lock_acquire+0x12e/0x410 [ 26.994326] __might_fault+0x14a/0x1d0 [ 26.998701] ashmem_ioctl+0x3c0/0xfe0 [ 27.002988] do_vfs_ioctl+0x1aa/0x1140 [ 27.007373] SyS_ioctl+0x8f/0xc0 [ 27.011239] do_syscall_64+0x1a4/0x490 [ 27.015619] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.021221] [ 27.021221] other info that might help us debug this: [ 27.021221] [ 27.029331] Possible unsafe locking scenario: [ 27.029331] [ 27.035354] CPU0 CPU1 [ 27.039989] ---- ---- [ 27.044630] lock(ashmem_mutex); [ 27.048294] lock(&mm->mmap_sem); [ 27.054549] lock(ashmem_mutex); [ 27.060721] lock(&mm->mmap_sem); [ 27.064467] [ 27.064467] *** DEADLOCK *** [ 27.064467] [ 27.070494] 1 lock held by syzkaller153371/3744: [ 27.075227] #0: (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 27.084184] [ 27.084184] stack backtrace: [ 27.088652] CPU: 1 PID: 3744 Comm: syzkaller153371 Not tainted 4.9.88-gbb52bba #59 [ 27.096336] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.105663] ffff8801d8f57908 ffffffff81d95f19 ffffffff853a5c00 ffffffff853a5c00 [ 27.113636] ffffffff853c4f80 ffff8801d8d620d8 ffff8801d8d61800 ffff8801d8f57950 [ 27.121606] ffffffff81238bd1 ffff8801d8d620d8 00000000d8d620b0 ffff8801d8d620d8 [ 27.129575] Call Trace: [ 27.132134] [] dump_stack+0xc1/0x128 [ 27.137468] [] print_circular_bug+0x271/0x310 [ 27.143592] [] __lock_acquire+0x2bf9/0x3640 [ 27.149544] [] ? trace_hardirqs_on_caller+0x38b/0x590 [ 27.156366] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 27.163350] [] ? mark_held_locks+0xaf/0x100 [ 27.169302] [] ? mutex_lock_nested+0x5e3/0x870 [ 27.175506] [] ? __lock_is_held+0xa1/0xf0 [ 27.181273] [] lock_acquire+0x12e/0x410 [ 27.186865] [] ? __might_fault+0xe4/0x1d0 [ 27.192631] [] __might_fault+0x14a/0x1d0 [ 27.198323] [] ? __might_fault+0xe4/0x1d0 [ 27.204090] [] ashmem_ioctl+0x3c0/0xfe0 [ 27.209682] [] ? _raw_spin_unlock_irqrestore+0x5a/0x70 [ 27.216579] [] ? trace_hardirqs_on_caller+0x38b/0x590 [ 27.223401] [] ? get_name+0x250/0x250 [ 27.228822] [] ? get_name+0x250/0x250 [ 27.234254] [] do_vfs_ioctl+0x1aa/0x1140 [ 27.239939] [] ? ioctl_preallocate+0x220/0x220 [ 27.246141] [] ? selinux_file_ioctl+0x355/0x530 [ 27.252427] [] ? selinux_capable+0x40/0x40 [ 27.258292] [] ? __fget+0x20a/0x3b0 executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program [ 27.263536] [] ? __fget+0x231/0x3b0 [ 27.268790] [] ? __fget+0x47/0x3b0 [ 27.273957] [] ? security_file_ioctl+0x89/0xb0 [ 27.280165] [] SyS_ioctl+0x8f/0xc0 [ 27.285323] [] ? do_vfs_ioctl+0x1140/0x1140 [ 27.291273] [] do_syscall_64+0x1a4/0x490 [ 27.296953] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program