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Description of problem: Calling a subshell within a script started by exec can cause the exec'ed script to call itself indefinitely, much like a fork bomb. Note: be careful with the test case, as it may make your system unstable. Version-Release number of selected component (if applicable): ksh-20100621-5.el5 How reproducible: 100% of the time Steps to Reproduce: 1. Create an executable file "foo" with the following two strings: $ cat /root/foo vi /tmp/bar # Comment needed to trigger the bomb 2. Start a KSH session and exec the foo script: $ ksh $ exec /root/foo 3. You are now in a VI session. Send the TSTP signal to VI using CTRL-Z, close VI using :q. Actual results: /root/foo spawns itself as a child until it hits the nproc limit and is unable to fork any more processes. Expected results: The VI session drops to the background and can be recalled using "fg". Additional info: Unable to reproduce using bash. Still reproduces using the updated KSH RPM's from bug https://bugzilla.redhat.com/show_bug.cgi?id=892206
Some more information on how the processes look: $ ps -ef --forest root 4741 1 0 20:11 pts/0 00:00:00 /root/foo root 4742 4741 0 20:11 pts/0 00:00:00 \_ /root/foo root 4743 4742 0 20:11 pts/0 00:00:00 \_ /root/foo root 4744 4743 0 20:11 pts/0 00:00:00 \_ /root/foo root 4745 4744 0 20:11 pts/0 00:00:00 \_ /root/foo ...
thanks for reporting reproducible
Reproduces in RHEL6 as well: $ ksh --version version sh (AT&T Research) 93t+ 2010-06-21 $ rpm -qa |grep ksh ksh-20100621-19.el6.x86_64 On RHEL6 the script sometimes gives a Memory fault without spawning unlimited childs: $ exec /root/foo /root/foo: line 1: 0: /root/foo: line 1: 2396: Memory fault
There is already another ksh fork bomb bug reported for RHEL5 - bug #910923 Instead of closing this as a duplicate, I'll use it for tracking this bug in RHEL6
I'm not authorized to see that bug, I guess that is why it missed the search. Any details on the bug (hunting) yet?
(In reply to comment #5) > Any details on the bug (hunting) yet? We have patch ready for next update
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. http://rhn.redhat.com/errata/RHBA-2013-1599.html