[....] Starting enhanced syslogd: rsyslogd[ 13.261393] audit: type=1400 audit(1519646268.710:4): avc: denied { syslog } for pid=3647 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 OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting file context maintaining daemon: restorecond[?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.15.192' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 26.388370] [ 26.390025] ====================================================== [ 26.396310] [ INFO: possible circular locking dependency detected ] [ 26.402684] 4.9.84-ga9d0273 #52 Not tainted [ 26.406970] ------------------------------------------------------- [ 26.413343] syzkaller339600/3803 is trying to acquire lock: [ 26.419020] (&mm->mmap_sem){++++++}, at: [] __might_fault+0xe4/0x1d0 [ 26.427483] but task is already holding lock: [ 26.432120] (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 26.440497] which lock already depends on the new lock. [ 26.440497] [ 26.447476] [ 26.447476] the existing dependency chain (in reverse order) is: [ 26.455064] -> #1 (ashmem_mutex){+.+.+.}: [ 26.459823] lock_acquire+0x12e/0x410 [ 26.464123] mutex_lock_nested+0xbb/0x870 [ 26.468762] ashmem_mmap+0x53/0x400 [ 26.472880] mmap_region+0x7dd/0xfd0 [ 26.477096] do_mmap+0x57b/0xbe0 [ 26.480961] vm_mmap_pgoff+0x16b/0x1b0 [ 26.485337] SyS_mmap_pgoff+0x33f/0x560 [ 26.489802] do_fast_syscall_32+0x2f5/0x870 [ 26.494613] entry_SYSENTER_compat+0x90/0xa2 [ 26.499508] -> #0 (&mm->mmap_sem){++++++}: [ 26.504354] __lock_acquire+0x2bf9/0x3640 [ 26.508992] lock_acquire+0x12e/0x410 [ 26.513282] __might_fault+0x14a/0x1d0 [ 26.517660] ashmem_ioctl+0x3c0/0xfe0 [ 26.521951] compat_ashmem_ioctl+0x3e/0x50 [ 26.526677] compat_SyS_ioctl+0x15f/0x2050 [ 26.531399] do_fast_syscall_32+0x2f5/0x870 [ 26.536209] entry_SYSENTER_compat+0x90/0xa2 [ 26.541102] [ 26.541102] other info that might help us debug this: [ 26.541102] [ 26.549211] Possible unsafe locking scenario: [ 26.549211] [ 26.555233] CPU0 CPU1 [ 26.559866] ---- ---- [ 26.564497] lock(ashmem_mutex); [ 26.568153] lock(&mm->mmap_sem); [ 26.574411] lock(ashmem_mutex); [ 26.580578] lock(&mm->mmap_sem); [ 26.584320] [ 26.584320] *** DEADLOCK *** [ 26.584320] [ 26.590344] 1 lock held by syzkaller339600/3803: [ 26.595067] #0: (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 26.603990] [ 26.603990] stack backtrace: [ 26.608455] CPU: 1 PID: 3803 Comm: syzkaller339600 Not tainted 4.9.84-ga9d0273 #52 [ 26.616128] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 26.625459] ffff8801d7aefa38 ffffffff81d956b9 ffffffff853a2cd0 ffffffff853a2cd0 [ 26.633441] ffffffff853c2f80 ffff8801d90808d8 ffff8801d9080000 ffff8801d7aefa80 [ 26.641408] ffffffff812387f1 ffff8801d90808d8 00000000d90808b0 ffff8801d90808d8 [ 26.649374] Call Trace: [ 26.651930] [] dump_stack+0xc1/0x128 [ 26.657264] [] print_circular_bug+0x271/0x310 [ 26.663376] [] __lock_acquire+0x2bf9/0x3640 [ 26.669317] [] ? avc_has_extended_perms+0x3fc/0xf10 [ 26.675951] [] ? avc_has_extended_perms+0xe2/0xf10 [ 26.682500] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 26.689486] [] ? mark_held_locks+0xaf/0x100 [ 26.695427] [] ? mutex_lock_nested+0x5e3/0x870 [ 26.701626] [] ? __lock_is_held+0xa1/0xf0 [ 26.707390] [] lock_acquire+0x12e/0x410 [ 26.712983] [] ? __might_fault+0xe4/0x1d0 [ 26.718748] [] __might_fault+0x14a/0x1d0 [ 26.724428] [] ? __might_fault+0xe4/0x1d0 [ 26.730192] [] ashmem_ioctl+0x3c0/0xfe0 [ 26.735784] [] ? selinux_file_ioctl+0x355/0x530 [ 26.742072] [] ? selinux_capable+0x40/0x40 [ 26.747924] [] ? get_name+0x250/0x250 [ 26.753344] [] compat_ashmem_ioctl+0x3e/0x50 [ 26.759372] [] compat_SyS_ioctl+0x15f/0x2050 [ 26.765397] [] ? ashmem_ioctl+0xfe0/0xfe0 [ 26.771161] [] ? do_ioctl+0x60/0x60 [ 26.776409] [] do_fast_syscall_32+0x2f5/0x870 [ 26.782525] [] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 26.78916