[....] Starting enhanced syslogd: rsyslogd[ 12.135146] audit: type=1400 audit(1521173934.311:4): avc: denied { syslog } for pid=3642 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 '10.128.0.39' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 27.561088] [ 27.562716] ====================================================== [ 27.569007] [ INFO: possible circular locking dependency detected ] [ 27.575402] 4.9.87-gd6f2774 #57 Not tainted [ 27.579699] ------------------------------------------------------- [ 27.586069] syzkaller945041/3801 is trying to acquire lock: [ 27.591747] (&mm->mmap_sem){++++++}, at: [] __might_fault+0xe4/0x1d0 [ 27.600209] but task is already holding lock: [ 27.604841] (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 27.613214] which lock already depends on the new lock. [ 27.613214] [ 27.620193] [ 27.620193] the existing dependency chain (in reverse order) is: [ 27.627780] -> #1 (ashmem_mutex){+.+.+.}: [ 27.632537] lock_acquire+0x12e/0x410 [ 27.636827] mutex_lock_nested+0xbb/0x870 [ 27.641467] ashmem_mmap+0x53/0x400 [ 27.645598] mmap_region+0x7dd/0xfd0 [ 27.649801] do_mmap+0x57b/0xbe0 [ 27.653656] vm_mmap_pgoff+0x16b/0x1b0 [ 27.658037] SyS_mmap_pgoff+0x33f/0x560 [ 27.662502] SyS_mmap+0x16/0x20 [ 27.666273] do_syscall_64+0x1a4/0x490 [ 27.670652] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.676239] -> #0 (&mm->mmap_sem){++++++}: [ 27.681098] __lock_acquire+0x2bf9/0x3640 [ 27.685733] lock_acquire+0x12e/0x410 [ 27.690023] __might_fault+0x14a/0x1d0 [ 27.694398] ashmem_ioctl+0x3c0/0xfe0 [ 27.698688] do_vfs_ioctl+0x1aa/0x1140 [ 27.703063] SyS_ioctl+0x8f/0xc0 [ 27.706917] do_syscall_64+0x1a4/0x490 [ 27.711303] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.716898] [ 27.716898] other info that might help us debug this: [ 27.716898] [ 27.725016] Possible unsafe locking scenario: [ 27.725016] [ 27.731041] CPU0 CPU1 [ 27.735675] ---- ---- [ 27.740313] lock(ashmem_mutex); [ 27.743994] lock(&mm->mmap_sem); [ 27.750280] lock(ashmem_mutex); [ 27.756456] lock(&mm->mmap_sem); [ 27.760200] [ 27.760200] *** DEADLOCK *** [ 27.760200] [ 27.766235] 1 lock held by syzkaller945041/3801: [ 27.770961] #0: (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 27.779885] [ 27.779885] stack backtrace: [ 27.784351] CPU: 1 PID: 3801 Comm: syzkaller945041 Not tainted 4.9.87-gd6f2774 #57 [ 27.792023] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.801346] ffff8801c0567908 ffffffff81d95bd9 ffffffff853a4cd0 ffffffff853a4cd0 [ 27.809306] ffffffff853c4a70 ffff8801d8f450d8 ffff8801d8f44800 ffff8801c0567950 [ 27.817272] ffffffff81238961 ffff8801d8f450d8 00000000d8f450b0 ffff8801d8f450d8 [ 27.825240] Call Trace: [ 27.827798] [] dump_stack+0xc1/0x128 [ 27.833133] [] print_circular_bug+0x271/0x310 [ 27.839261] [] __lock_acquire+0x2bf9/0x3640 [ 27.845199] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 27.852188] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 27.859177] [] ? mark_held_locks+0xaf/0x100 [ 27.865121] [] ? mutex_lock_nested+0x5e3/0x870 [ 27.871320] [] ? __lock_is_held+0xa1/0xf0 [ 27.877083] [] lock_acquire+0x12e/0x410 [ 27.882683] [] ? __might_fault+0xe4/0x1d0 [ 27.888452] [] __might_fault+0x14a/0x1d0 [ 27.894131] [] ? __might_fault+0xe4/0x1d0 [ 27.899899] [] ashmem_ioctl+0x3c0/0xfe0 [ 27.905491] [] ? vma_wants_writenotify+0x51/0x380 [ 27.911949] [] ? vma_set_page_prot+0x10f/0x180 [ 27.918155] [] ? get_name+0x250/0x250 [ 27.923574] [] ? mmap_region+0x161/0xfd0 [ 27.929258] [] ? get_name+0x250/0x250 [ 27.934689] [] do_vfs_ioctl+0x1aa/0x1140 [ 27.940370] [] ? ioctl_preallocate+0x220/0x220 [ 27.946568] [] ? selinux_file_ioctl+0x355/0x530 [ 27.952851] [] ? selinux_capable+0x40/0x40 [ 27.958708] [] ? fput+0xd2