[....] Starting enhanced syslogd: rsyslogd[ 15.460647] audit: type=1400 audit(1519645446.589:4): 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 mcstransd: [....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] 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 '10.128.15.227' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 28.435765] [ 28.437465] ====================================================== [ 28.443755] [ INFO: possible circular locking dependency detected ] [ 28.450135] 4.9.84-ga9d0273 #52 Not tainted [ 28.454436] ------------------------------------------------------- [ 28.460815] syzkaller645152/3803 is trying to acquire lock: [ 28.466513] (&mm->mmap_sem){++++++}, at: [] __might_fault+0xe4/0x1d0 [ 28.475001] but task is already holding lock: [ 28.479649] (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 28.488053] which lock already depends on the new lock. [ 28.488053] [ 28.495035] [ 28.495035] the existing dependency chain (in reverse order) is: [ 28.502622] -> #1 (ashmem_mutex){+.+.+.}: [ 28.507393] lock_acquire+0x12e/0x410 [ 28.511686] mutex_lock_nested+0xbb/0x870 [ 28.516327] ashmem_mmap+0x53/0x400 [ 28.520449] mmap_region+0x7dd/0xfd0 [ 28.524669] do_mmap+0x57b/0xbe0 [ 28.528526] vm_mmap_pgoff+0x16b/0x1b0 [ 28.532903] SyS_mmap_pgoff+0x33f/0x560 [ 28.537456] do_fast_syscall_32+0x2f5/0x870 [ 28.542266] entry_SYSENTER_compat+0x90/0xa2 [ 28.547163] -> #0 (&mm->mmap_sem){++++++}: [ 28.552038] __lock_acquire+0x2bf9/0x3640 [ 28.556674] lock_acquire+0x12e/0x410 [ 28.560977] __might_fault+0x14a/0x1d0 [ 28.565353] ashmem_ioctl+0x3c0/0xfe0 [ 28.569850] compat_ashmem_ioctl+0x3e/0x50 [ 28.574589] compat_SyS_ioctl+0x15f/0x2050 [ 28.579327] do_fast_syscall_32+0x2f5/0x870 [ 28.584144] entry_SYSENTER_compat+0x90/0xa2 [ 28.589038] [ 28.589038] other info that might help us debug this: [ 28.589038] [ 28.597149] Possible unsafe locking scenario: [ 28.597149] [ 28.603189] CPU0 CPU1 [ 28.607824] ---- ---- [ 28.612458] lock(ashmem_mutex); [ 28.616115] lock(&mm->mmap_sem); [ 28.622370] lock(ashmem_mutex); [ 28.628557] lock(&mm->mmap_sem); [ 28.632322] [ 28.632322] *** DEADLOCK *** [ 28.632322] [ 28.638351] 1 lock held by syzkaller645152/3803: [ 28.643072] #0: (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 28.652004] [ 28.652004] stack backtrace: [ 28.656470] CPU: 1 PID: 3803 Comm: syzkaller645152 Not tainted 4.9.84-ga9d0273 #52 [ 28.664157] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 28.673484] ffff8801d802fa38 ffffffff81d956b9 ffffffff853a3db0 ffffffff853a3db0 [ 28.681460] ffffffff853c28c0 ffff8801d7e568d8 ffff8801d7e56000 ffff8801d802fa80 [ 28.689434] ffffffff812387f1 ffff8801d7e568d8 00000000d7e568b0 ffff8801d7e568d8 [ 28.697409] Call Trace: [ 28.699970] [] dump_stack+0xc1/0x128 [ 28.705309] [] print_circular_bug+0x271/0x310 [ 28.711422] [] __lock_acquire+0x2bf9/0x3640 [ 28.717363] [] ? avc_has_extended_perms+0x3fc/0xf10 [ 28.723999] [] ? avc_has_extended_perms+0xe2/0xf10 [ 28.730552] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 28.737533] [] ? mark_held_locks+0xaf/0x100 [ 28.743476] [] ? mutex_lock_nested+0x5e3/0x870 [ 28.749681] [] ? __lock_is_held+0xa1/0xf0 [ 28.755449] [] lock_acquire+0x12e/0x410 [ 28.761045] [] ? __might_fault+0xe4/0x1d0 [ 28.766812] [] __might_fault+0x14a/0x1d0 [ 28.772494] [] ? __might_fault+0xe4/0x1d0 [ 28.778264] [] ashmem_ioctl+0x3c0/0xfe0 [ 28.783861] [] ? selinux_file_ioctl+0x355/0x530 [ 28.790148] [] ? selinux_capable+0x40/0x40 [ 28.796003] [] ? get_name+0x250/0x250 [ 28.801422] [] compat_ashmem_ioctl+0x3e/0x50 [ 28.807453] [] compat_SyS_ioctl+0x15f/0x2050 [ 28.813501] [] ? ashmem_ioctl+0xfe0/0xfe0 [ 28.819269] [] ? do_ioctl+0x60/0x60 [ 28.824518] [] do_fast_syscall_32+0x2f5/0x870 [ 28.830635] [] ? trace_hardirqs_off_thunk+0x1a/0x1c [