[....] Starting enhanced syslogd: rsyslogd[ 12.552446] audit: type=1400 audit(1519943230.655:4): avc: denied { syslog } for pid=3644 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 '10.128.0.18' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 19.990709] [ 19.992372] ====================================================== [ 19.998659] [ INFO: possible circular locking dependency detected ] [ 20.005032] 4.9.85-g4c4262a #47 Not tainted [ 20.009320] ------------------------------------------------------- [ 20.015700] syzkaller956587/3792 is trying to acquire lock: [ 20.021379] (&mm->mmap_sem){++++++}, at: [] __might_fault+0xe4/0x1d0 [ 20.029857] but task is already holding lock: [ 20.034502] (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 20.042889] which lock already depends on the new lock. [ 20.042889] [ 20.049870] [ 20.049870] the existing dependency chain (in reverse order) is: [ 20.057461] -> #1 (ashmem_mutex){+.+.+.}: [ 20.062233] lock_acquire+0x12e/0x410 [ 20.066528] mutex_lock_nested+0xbb/0x870 [ 20.071169] ashmem_mmap+0x53/0x400 [ 20.075287] mmap_region+0x7dd/0xfd0 [ 20.079488] do_mmap+0x57b/0xbe0 [ 20.083345] vm_mmap_pgoff+0x16b/0x1b0 [ 20.087722] SyS_mmap_pgoff+0x33f/0x560 [ 20.092185] SyS_mmap+0x16/0x20 [ 20.095958] do_syscall_64+0x1a4/0x490 [ 20.100335] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 20.105927] -> #0 (&mm->mmap_sem){++++++}: [ 20.110783] __lock_acquire+0x2bf9/0x3640 [ 20.115419] lock_acquire+0x12e/0x410 [ 20.119713] __might_fault+0x14a/0x1d0 [ 20.124089] ashmem_ioctl+0x3c0/0xfe0 [ 20.128379] do_vfs_ioctl+0x1aa/0x1140 [ 20.132756] SyS_ioctl+0x8f/0xc0 [ 20.136615] do_syscall_64+0x1a4/0x490 [ 20.141004] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 20.146595] [ 20.146595] other info that might help us debug this: [ 20.146595] [ 20.154707] Possible unsafe locking scenario: [ 20.154707] [ 20.160731] CPU0 CPU1 [ 20.165365] ---- ---- [ 20.169996] lock(ashmem_mutex); [ 20.173649] lock(&mm->mmap_sem); [ 20.179907] lock(ashmem_mutex); [ 20.186077] lock(&mm->mmap_sem); [ 20.189815] [ 20.189815] *** DEADLOCK *** [ 20.189815] [ 20.195843] 1 lock held by syzkaller956587/3792: [ 20.200565] #0: (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 20.209503] [ 20.209503] stack backtrace: [ 20.213974] CPU: 1 PID: 3792 Comm: syzkaller956587 Not tainted 4.9.85-g4c4262a #47 [ 20.221648] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 20.230975] ffff8801d871f908 ffffffff81d95739 ffffffff853a2cd0 ffffffff853a2cd0 [ 20.238948] ffffffff853c2dd0 ffff8801d85d08d8 ffff8801d85d0000 ffff8801d871f950 [ 20.246922] ffffffff812387f1 ffff8801d85d08d8 00000000d85d08b0 ffff8801d85d08d8 [ 20.254890] Call Trace: [ 20.257457] [] dump_stack+0xc1/0x128 [ 20.262793] [] print_circular_bug+0x271/0x310 [ 20.268906] [] __lock_acquire+0x2bf9/0x3640 [ 20.274850] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 20.281918] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 20.288901] [] ? mark_held_locks+0xaf/0x100 [ 20.294844] [] ? mutex_lock_nested+0x5e3/0x870 [ 20.301043] [] ? __lock_is_held+0xa1/0xf0 [ 20.306826] [] lock_acquire+0x12e/0x410 [ 20.312428] [] ? __might_fault+0xe4/0x1d0 [ 20.318198] [] __might_fault+0x14a/0x1d0 [ 20.323882] [] ? __might_fault+0xe4/0x1d0 [ 20.329666] [] ashmem_ioctl+0x3c0/0xfe0 [ 20.335260] [] ? vma_wants_writenotify+0x51/0x380 [ 20.341730] [] ? vma_set_page_prot+0x10f/0x180 [ 20.347934] [] ? get_name+0x250/0x250 [ 20.353353] [] ? mmap_region+0x161/0xfd0 [ 20.359042] [] ? get_name+0x250/0x250 [ 20.364466] [] do_vfs_ioctl+0x1aa/0x1140 [ 20.370147] [] ? ioctl_preallocate+0x220/0x220 [ 20.376350] [] ? selinux_file_ioctl+0x355/0x530 [ 20.382642] [] ? selinux_capable+0x40/0x40 [ 20.388512] [] ? fput+0xd