The rw_vm function in usercopy.c in the 4GB split patch for the Linux kernel in Red Hat Enterprise Linux 4 does not perform proper bounds checking, which allows local users to cause a denial of service (crash).
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A11556
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=165547