[....] Starting enhanced syslogd: rsyslogd[ 13.801682] audit: type=1400 audit(1519679755.961:4): avc: denied { syslog } for pid=3646 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 '10.128.15.199' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 26.663260] [ 26.665029] ====================================================== [ 26.671327] [ INFO: possible circular locking dependency detected ] [ 26.677705] 4.9.84-ga9d0273 #44 Not tainted [ 26.681994] ------------------------------------------------------- [ 26.688368] syzkaller157188/3804 is trying to acquire lock: [ 26.694070] (&mm->mmap_sem){++++++}, at: [] __might_fault+0xe4/0x1d0 [ 26.702556] but task is already holding lock: [ 26.707197] (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 26.715586] which lock already depends on the new lock. [ 26.715586] [ 26.722579] [ 26.722579] the existing dependency chain (in reverse order) is: [ 26.730172] -> #1 (ashmem_mutex){+.+.+.}: [ 26.734945] lock_acquire+0x12e/0x410 [ 26.739238] mutex_lock_nested+0xbb/0x870 [ 26.743877] ashmem_mmap+0x53/0x400 [ 26.748003] mmap_region+0x7dd/0xfd0 [ 26.752207] do_mmap+0x57b/0xbe0 [ 26.756067] vm_mmap_pgoff+0x16b/0x1b0 [ 26.760445] SyS_mmap_pgoff+0x33f/0x560 [ 26.764910] SyS_mmap+0x16/0x20 [ 26.768683] do_syscall_64+0x1a4/0x490 [ 26.773063] entry_SYSCALL_64_after_swapgs+0x47/0xc5 [ 26.778655] -> #0 (&mm->mmap_sem){++++++}: [ 26.783513] __lock_acquire+0x2bf9/0x3640 [ 26.788152] lock_acquire+0x12e/0x410 [ 26.792446] __might_fault+0x14a/0x1d0 [ 26.796827] ashmem_ioctl+0x3c0/0xfe0 [ 26.801121] do_vfs_ioctl+0x1aa/0x1140 [ 26.805516] SyS_ioctl+0x8f/0xc0 [ 26.809376] do_syscall_64+0x1a4/0x490 [ 26.813756] entry_SYSCALL_64_after_swapgs+0x47/0xc5 [ 26.819349] [ 26.819349] other info that might help us debug this: [ 26.819349] [ 26.827461] Possible unsafe locking scenario: [ 26.827461] [ 26.833488] CPU0 CPU1 [ 26.838125] ---- ---- [ 26.842762] lock(ashmem_mutex); [ 26.846426] lock(&mm->mmap_sem); [ 26.852689] lock(ashmem_mutex); [ 26.858861] lock(&mm->mmap_sem); [ 26.862606] [ 26.862606] *** DEADLOCK *** [ 26.862606] [ 26.868636] 1 lock held by syzkaller157188/3804: [ 26.873372] #0: (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 26.882316] [ 26.882316] stack backtrace: [ 26.886785] CPU: 0 PID: 3804 Comm: syzkaller157188 Not tainted 4.9.84-ga9d0273 #44 [ 26.894470] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 26.903798] ffff8801d7c47908 ffffffff81d956b9 ffffffff853a2cd0 ffffffff853a2cd0 [ 26.911791] ffffffff853c2f80 ffff8801d939a0d8 ffff8801d9399800 ffff8801d7c47950 [ 26.919770] ffffffff812387f1 ffff8801d939a0d8 00000000d939a0b0 ffff8801d939a0d8 [ 26.927751] Call Trace: [ 26.930309] [] dump_stack+0xc1/0x128 [ 26.935646] [] print_circular_bug+0x271/0x310 [ 26.941765] [] __lock_acquire+0x2bf9/0x3640 [ 26.947718] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 26.954709] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 26.961696] [] ? mark_held_locks+0xaf/0x100 [ 26.967642] [] ? mutex_lock_nested+0x5e3/0x870 [ 26.973844] [] ? __lock_is_held+0xa1/0xf0 [ 26.979614] [] lock_acquire+0x12e/0x410 [ 26.985208] [] ? __might_fault+0xe4/0x1d0 [ 26.990978] [] __might_fault+0x14a/0x1d0 [ 26.996661] [] ? __might_fault+0xe4/0x1d0 [ 27.002436] [] ashmem_ioctl+0x3c0/0xfe0 [ 27.008032] [] ? vma_wants_writenotify+0x51/0x380 [ 27.014494] [] ? vma_set_page_prot+0x10f/0x180 [ 27.020702] [] ? get_name+0x250/0x250 [ 27.026124] [] ? mmap_region+0x161/0xfd0 [ 27.031804] [] ? get_name+0x250/0x250 [ 27.037227] [] do_vfs_ioctl+0x1aa/0x1140 [ 27.042909] [] ? ioctl_preallocate+0x220/0x220 [ 27.049110] [] ? selinux_file_ioctl+0x355/0x530 [ 27.055400] [] ? selinux_capable+0x40/0x40 [ 27.061256] [] ? fput+