[....] Starting enhanced syslogd: rsyslogd[ 11.647348] audit: type=1400 audit(1521303619.894:4): avc: denied { syslog } for pid=3631 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 OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting file context maintaining daemon: restorecond[?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.0.15' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 29.250282] [ 29.251916] ====================================================== [ 29.258198] [ INFO: possible circular locking dependency detected ] [ 29.264568] 4.9.87-gfc8bd0f #58 Not tainted [ 29.268851] ------------------------------------------------------- [ 29.275217] syzkaller028250/3790 is trying to acquire lock: [ 29.280888] (&mm->mmap_sem){++++++}, at: [] __might_fault+0xe4/0x1d0 [ 29.289344] but task is already holding lock: [ 29.293974] (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 29.302342] which lock already depends on the new lock. [ 29.302342] [ 29.309318] [ 29.309318] the existing dependency chain (in reverse order) is: [ 29.316901] -> #1 (ashmem_mutex){+.+.+.}: [ 29.321649] lock_acquire+0x12e/0x410 [ 29.325935] mutex_lock_nested+0xbb/0x870 [ 29.330568] ashmem_mmap+0x53/0x400 [ 29.334681] mmap_region+0x7dd/0xfd0 [ 29.338880] do_mmap+0x57b/0xbe0 [ 29.342736] vm_mmap_pgoff+0x16b/0x1b0 [ 29.347111] SyS_mmap_pgoff+0x33f/0x560 [ 29.351570] SyS_mmap+0x16/0x20 [ 29.355338] do_syscall_64+0x1a4/0x490 [ 29.359710] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 29.365298] -> #0 (&mm->mmap_sem){++++++}: [ 29.370128] __lock_acquire+0x2bf9/0x3640 [ 29.374762] lock_acquire+0x12e/0x410 [ 29.379047] __might_fault+0x14a/0x1d0 [ 29.383419] ashmem_ioctl+0x3c0/0xfe0 [ 29.387707] do_vfs_ioctl+0x1aa/0x1140 [ 29.392081] SyS_ioctl+0x8f/0xc0 [ 29.395933] do_syscall_64+0x1a4/0x490 [ 29.400304] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 29.405892] [ 29.405892] other info that might help us debug this: [ 29.405892] [ 29.413996] Possible unsafe locking scenario: [ 29.413996] [ 29.420020] CPU0 CPU1 [ 29.424653] ---- ---- [ 29.429282] lock(ashmem_mutex); [ 29.432934] lock(&mm->mmap_sem); [ 29.439187] lock(ashmem_mutex); [ 29.445352] lock(&mm->mmap_sem); [ 29.449083] [ 29.449083] *** DEADLOCK *** [ 29.449083] [ 29.455105] 1 lock held by syzkaller028250/3790: [ 29.459822] #0: (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 29.468736] [ 29.468736] stack backtrace: [ 29.473201] CPU: 1 PID: 3790 Comm: syzkaller028250 Not tainted 4.9.87-gfc8bd0f #58 [ 29.480873] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 29.490192] ffff8801d875f908 ffffffff81d95bd9 ffffffff853a4b20 ffffffff853a4b20 [ 29.498146] ffffffff853c4710 ffff8801b98fe8d8 ffff8801b98fe000 ffff8801d875f950 [ 29.506103] ffffffff81238961 ffff8801b98fe8d8 00000000b98fe8b0 ffff8801b98fe8d8 [ 29.514061] Call Trace: [ 29.516617] [] dump_stack+0xc1/0x128 [ 29.521950] [] print_circular_bug+0x271/0x310 [ 29.528060] [] __lock_acquire+0x2bf9/0x3640 [ 29.533995] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 29.540972] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 29.547952] [] ? mark_held_locks+0xaf/0x100 [ 29.553889] [] ? mutex_lock_nested+0x5e3/0x870 [ 29.560085] [] ? __lock_is_held+0xa1/0xf0 [ 29.565846] [] lock_acquire+0x12e/0x410 [ 29.571435] [] ? __might_fault+0xe4/0x1d0 [ 29.577198] [] __might_fault+0x14a/0x1d0 [ 29.582872] [] ? __might_fault+0xe4/0x1d0 [ 29.588636] [] ashmem_ioctl+0x3c0/0xfe0 [ 29.594225] [] ? vma_wants_writenotify+0x51/0x380 [ 29.600680] [] ? vma_set_page_prot+0x10f/0x180 [ 29.606876] [] ? get_name+0x250/0x250 [ 29.612293] [] ? mmap_region+0x161/0xfd0 [ 29.617971] [] ? get_name+0x250/0x250 [ 29.623390] [] do_vfs_ioctl+0x1aa/0x1140 [ 29.629068] [] ? ioctl_preallocate+0x220/0x220 [ 29.635278] [] ? selinux_file_ioctl+0x355/0x530 [ 29.641563] [] ? selinux_capable+0x40/0x40 [ 29.647413] [] ? fput+0xd2/0x140