smbfs in Samba 3.5.8 and earlier attempts to use (1) mount.cifs to append to the /etc/mtab file and (2) umount.cifs to append to the /etc/mtab.tmp file without first checking whether resource limits would interfere, which allows local users to trigger corruption of the /etc/mtab file via a process with a small RLIMIT_FSIZE value, a related issue to CVE-2011-1089.