[....] Starting enhanced syslogd: rsyslogd[ 14.691015] audit: type=1400 audit(1520889691.875:4): 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 '10.128.0.45' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 26.100694] [ 26.102331] ====================================================== [ 26.108614] [ INFO: possible circular locking dependency detected ] [ 26.114986] 4.9.87-ga290494 #53 Not tainted [ 26.119272] ------------------------------------------------------- [ 26.125645] syzkaller380933/3803 is trying to acquire lock: [ 26.131325] (&mm->mmap_sem){++++++}, at: [] __might_fault+0xe4/0x1d0 [ 26.139788] but task is already holding lock: [ 26.144422] (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 26.152798] which lock already depends on the new lock. [ 26.152798] [ 26.159774] [ 26.159774] the existing dependency chain (in reverse order) is: [ 26.167360] -> #1 (ashmem_mutex){+.+.+.}: [ 26.172109] lock_acquire+0x12e/0x410 [ 26.176397] mutex_lock_nested+0xbb/0x870 [ 26.181030] ashmem_mmap+0x53/0x400 [ 26.185144] mmap_region+0x7dd/0xfd0 [ 26.189345] do_mmap+0x57b/0xbe0 [ 26.193201] vm_mmap_pgoff+0x16b/0x1b0 [ 26.197576] SyS_mmap_pgoff+0x33f/0x560 [ 26.202038] SyS_mmap+0x16/0x20 [ 26.205806] do_syscall_64+0x1a4/0x490 [ 26.210183] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 26.215769] -> #0 (&mm->mmap_sem){++++++}: [ 26.220603] __lock_acquire+0x2bf9/0x3640 [ 26.225235] lock_acquire+0x12e/0x410 [ 26.229524] __might_fault+0x14a/0x1d0 [ 26.233895] ashmem_ioctl+0x3c0/0xfe0 [ 26.238185] do_vfs_ioctl+0x1aa/0x1140 [ 26.242556] SyS_ioctl+0x8f/0xc0 [ 26.246409] do_syscall_64+0x1a4/0x490 [ 26.250782] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 26.256370] [ 26.256370] other info that might help us debug this: [ 26.256370] [ 26.264475] Possible unsafe locking scenario: [ 26.264475] [ 26.270497] CPU0 CPU1 [ 26.275128] ---- ---- [ 26.279760] lock(ashmem_mutex); [ 26.283403] lock(&mm->mmap_sem); [ 26.289658] lock(ashmem_mutex); [ 26.295825] lock(&mm->mmap_sem); [ 26.299555] [ 26.299555] *** DEADLOCK *** [ 26.299555] [ 26.305582] 1 lock held by syzkaller380933/3803: [ 26.310301] #0: (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 26.319231] [ 26.319231] stack backtrace: [ 26.323693] CPU: 0 PID: 3803 Comm: syzkaller380933 Not tainted 4.9.87-ga290494 #53 [ 26.331365] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 26.340688] ffff8801d995f908 ffffffff81d95a19 ffffffff853a5c00 ffffffff853a5c00 [ 26.348651] ffffffff853c48c0 ffff8801d93bd0d8 ffff8801d93bc800 ffff8801d995f950 [ 26.356617] ffffffff81238961 ffff8801d93bd0d8 00000000d93bd0b0 ffff8801d93bd0d8 [ 26.364584] Call Trace: [ 26.367141] [] dump_stack+0xc1/0x128 [ 26.372474] [] print_circular_bug+0x271/0x310 [ 26.378586] [] __lock_acquire+0x2bf9/0x3640 [ 26.384524] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 26.391505] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 26.398483] [] ? mark_held_locks+0xaf/0x100 [ 26.404425] [] ? mutex_lock_nested+0x5e3/0x870 [ 26.410620] [] ? __lock_is_held+0xa1/0xf0 [ 26.416381] [] lock_acquire+0x12e/0x410 [ 26.421970] [] ? __might_fault+0xe4/0x1d0 [ 26.427733] [] __might_fault+0x14a/0x1d0 [ 26.433411] [] ? __might_fault+0xe4/0x1d0 [ 26.439177] [] ashmem_ioctl+0x3c0/0xfe0 [ 26.444770] [] ? vma_wants_writenotify+0x51/0x380 [ 26.451239] [] ? vma_set_page_prot+0x10f/0x180 [ 26.457437] [] ? get_name+0x250/0x250 [ 26.462852] [] ? mmap_region+0x161/0xfd0 [ 26.468528] [] ? get_name+0x250/0x250 [ 26.473945] [] do_vfs_ioctl+0x1aa/0x1140 [ 26.479620] [] ? ioctl_preallocate+0x220/0x220 [ 26.485818] [] ? selinux_file_ioctl+0x355/0x530 [ 26.492101] [] ? selinux_capable+0x40/0x40 [ 26.497952] [] ? fput+0xd2/0x14