[....] Starting enhanced syslogd: rsyslogd[ 12.834875] audit: type=1400 audit(1520339334.427:4): avc: denied { syslog } for pid=3648 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 '10.128.0.23' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 24.313221] [ 24.314861] ====================================================== [ 24.321147] [ INFO: possible circular locking dependency detected ] [ 24.327515] 4.9.86-gb324a70 #50 Not tainted [ 24.331799] ------------------------------------------------------- [ 24.338169] syzkaller037451/3804 is trying to acquire lock: [ 24.343844] (&mm->mmap_sem){++++++}, at: [] __might_fault+0xe4/0x1d0 [ 24.352311] but task is already holding lock: [ 24.356943] (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 24.365312] which lock already depends on the new lock. [ 24.365312] [ 24.372292] [ 24.372292] the existing dependency chain (in reverse order) is: [ 24.379879] -> #1 (ashmem_mutex){+.+.+.}: [ 24.384638] lock_acquire+0x12e/0x410 [ 24.388928] mutex_lock_nested+0xbb/0x870 [ 24.393561] ashmem_mmap+0x53/0x400 [ 24.397677] mmap_region+0x7dd/0xfd0 [ 24.401878] do_mmap+0x57b/0xbe0 [ 24.405735] vm_mmap_pgoff+0x16b/0x1b0 [ 24.410108] SyS_mmap_pgoff+0x33f/0x560 [ 24.414571] SyS_mmap+0x16/0x20 [ 24.418341] do_syscall_64+0x1a4/0x490 [ 24.422717] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 24.428303] -> #0 (&mm->mmap_sem){++++++}: [ 24.433143] __lock_acquire+0x2bf9/0x3640 [ 24.437778] lock_acquire+0x12e/0x410 [ 24.442065] __might_fault+0x14a/0x1d0 [ 24.446440] ashmem_ioctl+0x3c0/0xfe0 [ 24.450727] do_vfs_ioctl+0x1aa/0x1140 [ 24.455101] SyS_ioctl+0x8f/0xc0 [ 24.458954] do_syscall_64+0x1a4/0x490 [ 24.463328] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 24.468915] [ 24.468915] other info that might help us debug this: [ 24.468915] [ 24.477021] Possible unsafe locking scenario: [ 24.477021] [ 24.483042] CPU0 CPU1 [ 24.487673] ---- ---- [ 24.492304] lock(ashmem_mutex); [ 24.495951] lock(&mm->mmap_sem); [ 24.502209] lock(ashmem_mutex); [ 24.508373] lock(&mm->mmap_sem); [ 24.512108] [ 24.512108] *** DEADLOCK *** [ 24.512108] [ 24.518134] 1 lock held by syzkaller037451/3804: [ 24.522852] #0: (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 24.531770] [ 24.531770] stack backtrace: [ 24.536232] CPU: 0 PID: 3804 Comm: syzkaller037451 Not tainted 4.9.86-gb324a70 #50 [ 24.543902] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 24.553227] ffff8801d8957908 ffffffff81d956f9 ffffffff853a4cd0 ffffffff853a4cd0 [ 24.561190] ffffffff853c4dd0 ffff8801b51c88d8 ffff8801b51c8000 ffff8801d8957950 [ 24.569158] ffffffff812387f1 ffff8801b51c88d8 00000000b51c88b0 ffff8801b51c88d8 [ 24.577118] Call Trace: [ 24.579672] [] dump_stack+0xc1/0x128 [ 24.585002] [] print_circular_bug+0x271/0x310 [ 24.591115] [] __lock_acquire+0x2bf9/0x3640 [ 24.597052] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 24.604032] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 24.611011] [] ? mark_held_locks+0xaf/0x100 [ 24.616948] [] ? mutex_lock_nested+0x5e3/0x870 [ 24.623145] [] ? __lock_is_held+0xa1/0xf0 [ 24.628907] [] lock_acquire+0x12e/0x410 [ 24.634499] [] ? __might_fault+0xe4/0x1d0 [ 24.640262] [] __might_fault+0x14a/0x1d0 [ 24.645941] [] ? __might_fault+0xe4/0x1d0 [ 24.651704] [] ashmem_ioctl+0x3c0/0xfe0 [ 24.657296] [] ? vma_wants_writenotify+0x51/0x380 [ 24.663752] [] ? vma_set_page_prot+0x10f/0x180 [ 24.669948] [] ? get_name+0x250/0x250 [ 24.675364] [] ? mmap_region+0x161/0xfd0 [ 24.681039] [] ? get_name+0x250/0x250 [ 24.686455] [] do_vfs_ioctl+0x1aa/0x1140 [ 24.692132] [] ? ioctl_preallocate+0x220/0x220 [ 24.698332] [] ? selinux_file_ioctl+0x355/0x530 [ 24.704618] [] ? selinux_capable+0x40/0x40 [ 24.710470] [] ? fput+0xd2/0x1