The clone system call in the Linux kernel 2.6.28 and earlier allows local users to send arbitrary signals to a parent process from an unprivileged child process by launching an additional child process with the CLONE_PARENT flag, and then letting this new process exit.
- http://www.ubuntu.com/usn/usn-751-1
- http://www.vmware.com/security/advisories/VMSA-2009-0016.html
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