[....] Starting enhanced syslogd: rsyslogd[ 16.259312] audit: type=1400 audit(1520496967.364:4): avc: denied { syslog } for pid=3649 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 '10.128.0.16' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 27.287187] [ 27.288833] ====================================================== [ 27.295119] [ INFO: possible circular locking dependency detected ] [ 27.301499] 4.9.86-gd3a2afb #51 Not tainted [ 27.305794] ------------------------------------------------------- [ 27.312178] syzkaller061903/3805 is trying to acquire lock: [ 27.317871] (&mm->mmap_sem){++++++}, at: [] __might_fault+0xe4/0x1d0 [ 27.326384] but task is already holding lock: [ 27.331023] (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 27.339444] which lock already depends on the new lock. [ 27.339444] [ 27.346436] [ 27.346436] the existing dependency chain (in reverse order) is: [ 27.354032] -> #1 (ashmem_mutex){+.+.+.}: [ 27.358807] lock_acquire+0x12e/0x410 [ 27.363107] mutex_lock_nested+0xbb/0x870 [ 27.367744] ashmem_mmap+0x53/0x400 [ 27.371862] mmap_region+0x7dd/0xfd0 [ 27.376068] do_mmap+0x57b/0xbe0 [ 27.379924] vm_mmap_pgoff+0x16b/0x1b0 [ 27.384299] SyS_mmap_pgoff+0x33f/0x560 [ 27.388763] SyS_mmap+0x16/0x20 [ 27.392535] do_syscall_64+0x1a4/0x490 [ 27.396928] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.402542] -> #0 (&mm->mmap_sem){++++++}: [ 27.407399] __lock_acquire+0x2bf9/0x3640 [ 27.412039] lock_acquire+0x12e/0x410 [ 27.416338] __might_fault+0x14a/0x1d0 [ 27.420716] ashmem_ioctl+0x3c0/0xfe0 [ 27.425015] do_vfs_ioctl+0x1aa/0x1140 [ 27.429405] SyS_ioctl+0x8f/0xc0 [ 27.433353] do_syscall_64+0x1a4/0x490 [ 27.437734] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.443322] [ 27.443322] other info that might help us debug this: [ 27.443322] [ 27.451434] Possible unsafe locking scenario: [ 27.451434] [ 27.457469] CPU0 CPU1 [ 27.462117] ---- ---- [ 27.466777] lock(ashmem_mutex); [ 27.470443] lock(&mm->mmap_sem); [ 27.476700] lock(ashmem_mutex); [ 27.482870] lock(&mm->mmap_sem); [ 27.486606] [ 27.486606] *** DEADLOCK *** [ 27.486606] [ 27.492636] 1 lock held by syzkaller061903/3805: [ 27.497357] #0: (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 27.506298] [ 27.506298] stack backtrace: [ 27.510770] CPU: 1 PID: 3805 Comm: syzkaller061903 Not tainted 4.9.86-gd3a2afb #51 [ 27.518445] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.527783] ffff8801b2fe7908 ffffffff81d956f9 ffffffff853a5db0 ffffffff853a5db0 [ 27.535793] ffffffff853c48c0 ffff8801d95120d8 ffff8801d9511800 ffff8801b2fe7950 [ 27.543770] ffffffff812387f1 ffff8801d95120d8 00000000d95120b0 ffff8801d95120d8 [ 27.551764] Call Trace: [ 27.554331] [] dump_stack+0xc1/0x128 [ 27.559666] [] print_circular_bug+0x271/0x310 [ 27.565794] [] __lock_acquire+0x2bf9/0x3640 [ 27.571739] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 27.578722] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 27.585705] [] ? mark_held_locks+0xaf/0x100 [ 27.591647] [] ? mutex_lock_nested+0x5e3/0x870 [ 27.597857] [] ? __lock_is_held+0xa1/0xf0 [ 27.603626] [] lock_acquire+0x12e/0x410 [ 27.609222] [] ? __might_fault+0xe4/0x1d0 [ 27.614990] [] __might_fault+0x14a/0x1d0 [ 27.620671] [] ? __might_fault+0xe4/0x1d0 [ 27.626459] [] ashmem_ioctl+0x3c0/0xfe0 [ 27.632057] [] ? vma_wants_writenotify+0x51/0x380 [ 27.638517] [] ? vma_set_page_prot+0x10f/0x180 [ 27.644716] [] ? get_name+0x250/0x250 [ 27.650139] [] ? mmap_region+0x161/0xfd0 [ 27.655819] [] ? get_name+0x250/0x250 [ 27.661240] [] do_vfs_ioctl+0x1aa/0x1140 [ 27.666920] [] ? ioctl_preallocate+0x220/0x220 [ 27.673122] [] ? selinux_file_ioctl+0x355/0x530 [ 27.679417] [] ? selinux_capable+0x40/0x40 [ 27.685280] [] ? fput