[....] Starting enhanced syslogd: rsyslogd[ 14.907040] audit: type=1400 audit(1520662211.252:4): avc: denied { syslog } for pid=3639 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 '10.128.0.49' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 27.513308] [ 27.514946] ====================================================== [ 27.521228] [ INFO: possible circular locking dependency detected ] [ 27.527599] 4.9.86-g00db063 #52 Not tainted [ 27.531883] ------------------------------------------------------- [ 27.538255] syzkaller940146/3795 is trying to acquire lock: [ 27.543932] (&mm->mmap_sem){++++++}, at: [] __might_fault+0xe4/0x1d0 [ 27.552402] but task is already holding lock: [ 27.557038] (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 27.565416] which lock already depends on the new lock. [ 27.565416] [ 27.572396] [ 27.572396] the existing dependency chain (in reverse order) is: [ 27.579985] -> #1 (ashmem_mutex){+.+.+.}: [ 27.584739] lock_acquire+0x12e/0x410 [ 27.589031] mutex_lock_nested+0xbb/0x870 [ 27.593666] ashmem_mmap+0x53/0x400 [ 27.597785] mmap_region+0x7dd/0xfd0 [ 27.601983] do_mmap+0x57b/0xbe0 [ 27.605837] vm_mmap_pgoff+0x16b/0x1b0 [ 27.610214] SyS_mmap_pgoff+0x33f/0x560 [ 27.614675] SyS_mmap+0x16/0x20 [ 27.618444] do_syscall_64+0x1a4/0x490 [ 27.622820] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.628405] -> #0 (&mm->mmap_sem){++++++}: [ 27.633246] __lock_acquire+0x2bf9/0x3640 [ 27.637882] lock_acquire+0x12e/0x410 [ 27.642257] __might_fault+0x14a/0x1d0 [ 27.646631] ashmem_ioctl+0x3c0/0xfe0 [ 27.650919] do_vfs_ioctl+0x1aa/0x1140 [ 27.655295] SyS_ioctl+0x8f/0xc0 [ 27.659147] do_syscall_64+0x1a4/0x490 [ 27.663519] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.669109] [ 27.669109] other info that might help us debug this: [ 27.669109] [ 27.677215] Possible unsafe locking scenario: [ 27.677215] [ 27.683237] CPU0 CPU1 [ 27.687871] ---- ---- [ 27.692501] lock(ashmem_mutex); [ 27.696153] lock(&mm->mmap_sem); [ 27.702407] lock(ashmem_mutex); [ 27.708588] lock(&mm->mmap_sem); [ 27.712325] [ 27.712325] *** DEADLOCK *** [ 27.712325] [ 27.718351] 1 lock held by syzkaller940146/3795: [ 27.723073] #0: (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 27.731994] [ 27.731994] stack backtrace: [ 27.736459] CPU: 0 PID: 3795 Comm: syzkaller940146 Not tainted 4.9.86-g00db063 #52 [ 27.744133] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.753456] ffff8801d8247908 ffffffff81d956f9 ffffffff853a5db0 ffffffff853a5db0 [ 27.761414] ffffffff853c4dd0 ffff8801b2d6e8d8 ffff8801b2d6e000 ffff8801d8247950 [ 27.769372] ffffffff812387f1 ffff8801b2d6e8d8 00000000b2d6e8b0 ffff8801b2d6e8d8 [ 27.777335] Call Trace: [ 27.779891] [] dump_stack+0xc1/0x128 [ 27.785234] [] print_circular_bug+0x271/0x310 [ 27.791357] [] __lock_acquire+0x2bf9/0x3640 [ 27.797298] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 27.804278] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 27.811257] [] ? mark_held_locks+0xaf/0x100 [ 27.817203] [] ? mutex_lock_nested+0x5e3/0x870 [ 27.823404] [] ? __lock_is_held+0xa1/0xf0 [ 27.829166] [] lock_acquire+0x12e/0x410 [ 27.834759] [] ? __might_fault+0xe4/0x1d0 [ 27.840523] [] __might_fault+0x14a/0x1d0 [ 27.846202] [] ? __might_fault+0xe4/0x1d0 [ 27.851966] [] ashmem_ioctl+0x3c0/0xfe0 [ 27.857556] [] ? vma_wants_writenotify+0x51/0x380 [ 27.864013] [] ? vma_set_page_prot+0x10f/0x180 [ 27.870212] [] ? get_name+0x250/0x250 [ 27.875628] [] ? mmap_region+0x161/0xfd0 [ 27.881305] [] ? get_name+0x250/0x250 [ 27.886729] [] do_vfs_ioctl+0x1aa/0x1140 [ 27.892407] [] ? ioctl_preallocate+0x220/0x220 [ 27.898612] [] ? selinux_file_ioctl+0x355/0x530 [ 27.904898] [] ? selinux_capable+0x40/0x40 [ 27.910749] [] ? fput+0xd2/0