[....] Starting enhanced syslogd: rsyslogd[ 13.105109] audit: type=1400 audit(1519638504.617:4): avc: denied { syslog } for pid=3559 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 '10.128.15.219' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 24.419315] [ 24.420958] ====================================================== [ 24.427249] [ INFO: possible circular locking dependency detected ] [ 24.433622] 4.9.84-ga9d0273 #52 Not tainted [ 24.437914] ------------------------------------------------------- [ 24.444291] syzkaller022836/3715 is trying to acquire lock: [ 24.449966] (&mm->mmap_sem){++++++}, at: [] __might_fault+0xe4/0x1d0 [ 24.458431] but task is already holding lock: [ 24.463067] (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 24.471453] which lock already depends on the new lock. [ 24.471453] [ 24.478432] [ 24.478432] the existing dependency chain (in reverse order) is: [ 24.486023] -> #1 (ashmem_mutex){+.+.+.}: [ 24.490784] lock_acquire+0x12e/0x410 [ 24.495075] mutex_lock_nested+0xbb/0x870 [ 24.499711] ashmem_mmap+0x53/0x400 [ 24.503829] mmap_region+0x7dd/0xfd0 [ 24.508032] do_mmap+0x57b/0xbe0 [ 24.511888] vm_mmap_pgoff+0x16b/0x1b0 [ 24.516270] SyS_mmap_pgoff+0x33f/0x560 [ 24.520732] do_fast_syscall_32+0x2f5/0x870 [ 24.525544] entry_SYSENTER_compat+0x90/0xa2 [ 24.530442] -> #0 (&mm->mmap_sem){++++++}: [ 24.535289] __lock_acquire+0x2bf9/0x3640 [ 24.539925] lock_acquire+0x12e/0x410 [ 24.544214] __might_fault+0x14a/0x1d0 [ 24.548589] ashmem_ioctl+0x3c0/0xfe0 [ 24.552878] compat_ashmem_ioctl+0x3e/0x50 [ 24.557603] compat_SyS_ioctl+0x15f/0x2050 [ 24.562328] do_fast_syscall_32+0x2f5/0x870 [ 24.567142] entry_SYSENTER_compat+0x90/0xa2 [ 24.572034] [ 24.572034] other info that might help us debug this: [ 24.572034] [ 24.580141] Possible unsafe locking scenario: [ 24.580141] [ 24.586165] CPU0 CPU1 [ 24.590799] ---- ---- [ 24.595437] lock(ashmem_mutex); [ 24.599093] lock(&mm->mmap_sem); [ 24.605346] lock(ashmem_mutex); [ 24.611510] lock(&mm->mmap_sem); [ 24.615241] [ 24.615241] *** DEADLOCK *** [ 24.615241] [ 24.621266] 1 lock held by syzkaller022836/3715: [ 24.625984] #0: (ashmem_mutex){+.+.+.}, at: [] ashmem_ioctl+0x371/0xfe0 [ 24.634911] [ 24.634911] stack backtrace: [ 24.639377] CPU: 0 PID: 3715 Comm: syzkaller022836 Not tainted 4.9.84-ga9d0273 #52 [ 24.647060] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 24.656388] ffff8801d8b07a38 ffffffff81d956b9 ffffffff853a2cd0 ffffffff853a2cd0 [ 24.664354] ffffffff853c2c20 ffff8801bf8ea0d8 ffff8801bf8e9800 ffff8801d8b07a80 [ 24.672322] ffffffff812387f1 ffff8801bf8ea0d8 00000000bf8ea0b0 ffff8801bf8ea0d8 [ 24.680289] Call Trace: [ 24.682849] [] dump_stack+0xc1/0x128 [ 24.688185] [] print_circular_bug+0x271/0x310 [ 24.694297] [] __lock_acquire+0x2bf9/0x3640 [ 24.700236] [] ? avc_has_extended_perms+0x3fc/0xf10 [ 24.706870] [] ? avc_has_extended_perms+0xe2/0xf10 [ 24.713422] [] ? debug_check_no_locks_freed+0x2c0/0x2c0 [ 24.720405] [] ? mark_held_locks+0xaf/0x100 [ 24.726348] [] ? mutex_lock_nested+0x5e3/0x870 [ 24.732548] [] ? __lock_is_held+0xa1/0xf0 [ 24.738311] [] lock_acquire+0x12e/0x410 [ 24.743905] [] ? __might_fault+0xe4/0x1d0 [ 24.749675] [] __might_fault+0x14a/0x1d0 [ 24.755380] [] ? __might_fault+0xe4/0x1d0 [ 24.761146] [] ashmem_ioctl+0x3c0/0xfe0 [ 24.766746] [] ? selinux_file_ioctl+0x355/0x530 [ 24.773040] [] ? selinux_capable+0x40/0x40 [ 24.778892] [] ? get_name+0x250/0x250 [ 24.784311] [] compat_ashmem_ioctl+0x3e/0x50 [ 24.790337] [] compat_SyS_ioctl+0x15f/0x2050 [ 24.796364] [] ? ashmem_ioctl+0xfe0/0xfe0 [ 24.802130] [] ? do_ioctl+0x60/0x60 [ 24.807375] [] do_fast_syscall_32+0x2f5/0x870 [ 24.813487] [] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 24.820120