From Chris Evans: It's a relatively minor signal issue where a child can send its parent process an arbitrary signal, even if the parent has a totally separate real and effective user id. This could be a nuisance in the case where long-running root daemons spawn direct child processes owned by untrusted users [*]. There may even be worse consequences if privileged processes have weak signal handling code for signals not normally triggerable by untrusted users.
man clone: The low byte of flags contains the number of the termination signal sent to the parent when the child dies. If this signal is specified as anything other than SIGCHLD, then the parent process must specify the __WALL or __WCLONE options when waiting for the child with wait(2). If no signal is specified, then the parent process is not signaled when the child terminates.
It's public now: http://scarybeastsecurity.blogspot.com/2009/02/linux-kernel-minor-signal-vulnerability.html
http://scary.beasts.org/security/CESA-2009-002.html
Created attachment 334735 [details] Upstream patch http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=2d5516cbb9daf7d0e342a2e3b0fc6f8c39a81205
This issue has been addressed in following products: Red Hat Enterprise Linux 5 Via RHSA-2009:0326 https://rhn.redhat.com/errata/RHSA-2009-0326.html
This issue has been addressed in following products: MRG for RHEL-5 Via RHSA-2009:0451 https://rhn.redhat.com/errata/RHSA-2009-0451.html
This issue has been addressed in following products: Red Hat Enterprise Linux 4 Via RHSA-2009:0459 https://rhn.redhat.com/errata/RHSA-2009-0459.html