michael at orlitzky
Jul 31, 2012, 7:12 PM
Views: 480
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pthread_create problems on hardened x86
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I've got an old problem with clamd, which creates a bunch of threads.
Every so often the logs will show e.g.,
Jul 31 06:01:41 mx1 clamd[24070]: pthread_create failed
Jul 31 06:01:41 mx1 clamd[24070]: pthread_create failed
Jul 31 06:01:41 mx1 clamd[24070]: pthread_create failed
Jul 31 06:01:41 mx1 clamd[24070]: pthread_create failed
It doesn't cause any noticeable problems, so I've sort of left it alone
but tonight I dug in a little. The problem seems (somehow) related to
that box's hardening.
I'm using a test program that creates a bunch of threads and then just
kills them. On the box in question,
# uname -a
Linux mx1 3.4.2-hardened #1 SMP Wed Jul 11 13:41:57 EDT 2012 i686
Intel(R) Xeon(TM) CPU 3.06GHz GenuineIntel GNU/Linux
# ./pthread_test 25
Creating 25 threads
Created thread #0...
Created thread #1...
Created thread #2...
Created thread #3...
pthread_create failed: Resource temporarily unavailable
Disabling all paxctl protections helps, but doesn't allow me to get all
the way to 25. I tried doing the protections one-at-a-time; it doesn't
really help:
# paxctl -pemrxs pthread_test
# ./pthread_test 25
Creating 25 threads
Created thread #0...
Created thread #1...
Created thread #2...
Created thread #3...
Created thread #4...
Created thread #5...
Created thread #6...
Created thread #7...
Created thread #8...
Created thread #9...
pthread_create failed: Resource temporarily unavailable
I get nothing in my dmesg, which otherwise records most limit-based denials.
Is there some way I can troubleshoot this? It works on amd64 with the
same kernel hardening options.
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pthread_create problems on hardened x86
