Multiple race conditions in the (1) mount.cifs and (2) umount.cifs programs in Samba 3.6 allow local users to cause a denial of service (mounting outage) via a SIGKILL signal during a time window when the /etc/mtab~ file exists.
https://www.openwall.com/lists/oss-security/2011/09/30/5
https://www.openwall.com/lists/oss-security/2011/09/27/1
https://git.samba.org/?p=cifs-utils.git%3Ba=commitdiff%3Bh=810f7e4e0f2dbcbee0294d9b371071cb08268200