From dmseg:
[50829.014469] audit: type=1326 audit(1541124906.429:11754): auid=4294967295 uid=600 gid=600 ses=4294967295 subj=u:r:minijail:s0 pid=18306 comm="cras" exe="/usr/bin/cras" sig=31 arch=c000003e syscall=25 compat=0 ip=0x7eb72d46d76a code=0x0

Syscall 25 is blocked by seccomp, which is mremap.

Use gdb to track the call of mremap:

Thread 1 "cras" hit Catchpoint 1 (call to syscall 25), 0x00007ffff713c76a in mremap () at ../sysdeps/unix/syscall-template.S:84
84      ../sysdeps/unix/syscall-template.S: No such file or directory.
(gdb) bt
#0  0x00007ffff713c76a in mremap () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007ffff70c0337 in mremap_chunk (p=p@entry=0x7ffff5a42000, new_size=4096, new_size@entry=32) at malloc.c:2875
#2  0x00007ffff70c5109 in __GI___libc_realloc (oldmem=0x7ffff5a42010, bytes=8) at malloc.c:3023
#3  0x00007ffff7f1022d in _dbus_string_compact () from /usr/lib64/libdbus-1.so.3
#4  0x00007ffff7f020ed in _dbus_message_loader_queue_messages () from /usr/lib64/libdbus-1.so.3
#5  0x00007ffff7f0a83e in ?? () from /usr/lib64/libdbus-1.so.3
#6  0x00007fffffffe0e0 in ?? ()
#7  0x0000000000000001 in ?? ()
#8  0x00007fffffffe060 in ?? ()
#9  0x0000000000000000 in ?? ()

Mremap is used when libdbus is calling realloc in dbus_string_compact(), which might not happen from a fresh restart.

Gdb command for debugging:

$ gdb cras
(gdb) catch syscall 25
(gdb) r

gdb with nostrip cras and dbus

Thread 1 "cras" hit Catchpoint 1 (call to syscall 25), 0x00007ffff713c76a in mremap () at ../sysdeps/unix/syscall-template.S:84
84      ../sysdeps/unix/syscall-template.S: No such file or directory.
(gdb) bt
#0  0x00007ffff713c76a in mremap () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007ffff70c0337 in mremap_chunk (p=p@entry=0x7ffff5a42000, new_size=4096, new_size@entry=32) at malloc.c:2875
#2  0x00007ffff70c5109 in __GI___libc_realloc (oldmem=0x7ffff5a42010, bytes=8) at malloc.c:3023
#3  0x00007ffff7f1022d in compact (real=0x555555765d68, max_waste=<optimized out>) at ../../dbus-1.10.12/dbus/dbus-string.c:294
#4  _dbus_string_compact (str=0x555555765d68, max_waste=<optimized out>) at ../../dbus-1.10.12/dbus/dbus-string.c:394
#5  0x00007ffff7f020ed in load_message (loader=<optimized out>, message=0x555555765dd0, byte_order=<optimized out>, 
    fields_array_len=<optimized out>, header_len=80, body_len=<optimized out>) at ../../dbus-1.10.12/dbus/dbus-message.c:4333
#6  _dbus_message_loader_queue_messages (loader=0x555555765d60) at ../../dbus-1.10.12/dbus/dbus-message.c:4404
#7  0x00007ffff7f0a83e in _dbus_transport_get_dispatch_status (transport=0x55555581aef0)
    at ../../dbus-1.10.12/dbus/dbus-transport.c:1122
#8  0x00007ffff7f0a8df in _dbus_transport_queue_messages (transport=0x55555581aef0)
    at ../../dbus-1.10.12/dbus/dbus-transport.c:1149
#9  0x00007ffff7f0bce7 in do_reading (transport=0x55555581aef0) at ../../dbus-1.10.12/dbus/dbus-transport-socket.c:891
#10 0x00007ffff7f0b3c0 in socket_handle_watch (transport=0x55555581aef0, watch=0x555555783dc0, flags=1)
    at ../../dbus-1.10.12/dbus/dbus-transport-socket.c:972
#11 0x00007ffff7f0a5d4 in _dbus_transport_handle_watch (transport=<optimized out>, watch=<optimized out>, condition=4096)
    at ../../dbus-1.10.12/dbus/dbus-transport.c:910
#12 0x00007ffff7eeea03 in _dbus_connection_handle_watch (watch=0x555555783dc0, condition=1, data=0x555555783a00)
    at ../../dbus-1.10.12/dbus/dbus-connection.c:1509
#13 0x0000555555564538 in dbus_watch_callback (arg=0x555555783dc0) at server/cras_dbus.c:37
#14 0x000055555555cd36 in cras_server_run (profile_disable_mask=<optimized out>) at server/cras_server.c:611
#15 0x000055555555c11e in main (argc=<optimized out>, argv=0x7fffffffe628) at server/cras.c:141

Send out CL (crrev.com/c/1314268) to fix this.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/third_party/adhd/+/e3b0bbc1487c486e503e828d75962882a7f71d8a

commit e3b0bbc1487c486e503e828d75962882a7f71d8a
Author: paulhsia <paulhsia@chromium.org>
Date: Fri Nov 02 21:50:44 2018

seccomp: Add mremap to policy file

Mremap is used when libdbus call realloc in __dbus_string_compact,
which might happen sometimes.

BUG= chromium:901225 
TEST=On a broken DUT
     $ restart cras
     and check if syscall 25 is blocked by seccomp in dmesg

Change-Id: Iaae7dc3e541305af66175bff39fcb481f636c403
Reviewed-on: https://chromium-review.googlesource.com/1314268
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Chih-Yang Hsia <paulhsia@chromium.org>
Reviewed-by: Cheng-Yi Chiang <cychiang@chromium.org>

[modify] https://crrev.com/e3b0bbc1487c486e503e828d75962882a7f71d8a/seccomp/cras-seccomp-arm64.policy
[modify] https://crrev.com/e3b0bbc1487c486e503e828d75962882a7f71d8a/seccomp/cras-seccomp-amd64.policy
[modify] https://crrev.com/e3b0bbc1487c486e503e828d75962882a7f71d8a/seccomp/cras-seccomp-arm.policy