[....] Starting enhanced syslogd: rsyslogd[ 12.623329] audit: type=1400 audit(1521118893.113:4): 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 '10.128.0.50' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 27.656780] [ 27.658432] ====================================================== [ 27.664714] [ INFO: possible circular locking dependency detected ] [ 27.671085] 4.9.87-g3a3a084 #56 Not tainted [ 27.675371] ------------------------------------------------------- [ 27.681859] syzkaller961201/3803 is trying to acquire lock: [ 27.687534] (&mm->mmap_sem){++++++}, at: [] __might_fault+0xe4/0x1d0 [ 27.695993] but task is already holding lock: [ 27.700626] (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 27.708994] which lock already depends on the new lock. [ 27.708994] [ 27.715973] [ 27.715973] the existing dependency chain (in reverse order) is: [ 27.723556] -> #1 (ashmem_mutex){+.+.+.}: [ 27.728308] lock_acquire+0x12e/0x410 [ 27.732599] mutex_lock_nested+0xbb/0x870 [ 27.737235] ashmem_mmap+0x53/0x400 [ 27.741349] mmap_region+0x7dd/0xfd0 [ 27.745547] do_mmap+0x57b/0xbe0 [ 27.749402] vm_mmap_pgoff+0x16b/0x1b0 [ 27.753778] SyS_mmap_pgoff+0x33f/0x560 [ 27.758240] SyS_mmap+0x16/0x20 [ 27.762008] do_syscall_64+0x1a4/0x490 [ 27.766382] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.771970] -> #0 (&mm->mmap_sem){++++++}: [ 27.776807] __lock_acquire+0x2bf9/0x3640 [ 27.781445] lock_acquire+0x12e/0x410 [ 27.785731] __might_fault+0x14a/0x1d0 [ 27.790104] ashmem_ioctl+0x3c0/0xfe0 [ 27.794394] do_vfs_ioctl+0x1aa/0x1140 [ 27.798766] SyS_ioctl+0x8f/0xc0 [ 27.802620] do_syscall_64+0x1a4/0x490 [ 27.806994] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.812580] [ 27.812580] other info that might help us debug this: [ 27.812580] [ 27.820684] Possible unsafe locking scenario: [ 27.820684] [ 27.826705] CPU0 CPU1 [ 27.831337] ---- ---- [ 27.835968] lock(ashmem_mutex); [ 27.839618] lock(&mm->mmap_sem); [ 27.845869] lock(ashmem_mutex); [ 27.852035] lock(&mm->mmap_sem); [ 27.855770] [ 27.855770] *** DEADLOCK *** [ 27.855770] [ 27.861797] 1 lock held by syzkaller961201/3803: [ 27.866519] #0: (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 27.875442] [ 27.875442] stack backtrace: [ 27.879906] CPU: 1 PID: 3803 Comm: syzkaller961201 Not tainted 4.9.87-g3a3a084 #56 [ 27.887843] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.897166] ffff8801d7487908 ffffffff81d95a19 ffffffff853a4cd0 ffffffff853a4cd0 [ 27.905130] ffffffff853c4f80 ffff8801d84e08d8 ffff8801d84e0000 ffff8801d7487950 [ 27.913088] ffffffff81238961 ffff8801d84e08d8 00000000d84e08b0 ffff8801d84e08d8 [ 27.921053] Call Trace: [ 27.923611] [] dump_stack+0xc1/0x128 [ 27.928945] [] print_circular_bug+0x271/0x310 [ 27.935056] [] __lock_acquire+0x2bf9/0x3640 [ 27.940994] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 27.947976] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 27.954953] [] ? mark_held_locks+0xaf/0x100 [ 27.960890] [] ? mutex_lock_nested+0x5e3/0x870 [ 27.967088] [] ? __lock_is_held+0xa1/0xf0 [ 27.972850] [] lock_acquire+0x12e/0x410 [ 27.978443] [] ? __might_fault+0xe4/0x1d0 [ 27.984209] [] __might_fault+0x14a/0x1d0 [ 27.989888] [] ? __might_fault+0xe4/0x1d0 [ 27.995651] [] ashmem_ioctl+0x3c0/0xfe0 [ 28.001240] [] ? vma_wants_writenotify+0x51/0x380 [ 28.007699] [] ? vma_set_page_prot+0x10f/0x180 [ 28.013896] [] ? get_name+0x250/0x250 [ 28.019315] [] ? mmap_region+0x161/0xfd0 [ 28.024991] [] ? get_name+0x250/0x250 [ 28.030412] [] do_vfs_ioctl+0x1aa/0x1140 [ 28.036088] [] ? ioctl_preallocate+0x220/0x220 [ 28.042283] [] ? selinux_file_ioctl+0x355/0x530 [ 28.048564] [] ? selinux_capable+0x40/0x40 [ 28.054414] [] ? fput+0xd2/