Bug 103049 - httpd hung up reading /dev/random
httpd hung up reading /dev/random
Product: Red Hat Raw Hide
Classification: Retired
Component: apr (Show other bugs)
All Linux
medium Severity medium
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Assigned To: Joe Orton
Depends On:
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Reported: 2003-08-25 16:44 EDT by matti aarnio
Modified: 2007-04-18 12:57 EDT (History)
1 user (show)

See Also:
Fixed In Version: 0.9.3-14
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2003-09-08 20:54:14 EDT
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oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
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Description matti aarnio 2003-08-25 16:44:46 EDT
Description of problem:
  Freshly updated  httpd  daemon hangs up during start.
  It turns out to be read() from  /dev/random  that is
  hanging in a server that does not (for some reason)
  accumulate much entropy..

Backtrace shows:
  0x403db8f8 in read () from /lib/i686/libpthread.so.0
  (gdb) where
  #0  0x403db8f8 in read () from /lib/i686/libpthread.so.0
  #1  0x40366190 in apr_proc_mutex_unix_flock_methods ()
     from /usr/lib/libapr-0.so.0
  #2  0x4002296a in _init () from /etc/httpd/modules/mod_auth_digest.so
  #3  0x40022afa in _init () from /etc/httpd/modules/mod_auth_digest.so
  #4  0x08067fca in ap_run_post_config ()
  #5  0x0806d648 in main ()
  #6  0x404368c7 in __libc_start_main () from /lib/i686/libc.so.6

Version-Release number of selected component (if applicable):

How reproducible:
  Up to date  kernel (2.4.21*nptlsmp)  and httpd
Actual results:
  Server hung-up

Expected results:
  Server running

Additional info:
  This is rather endemic problem in recent Rawhide things.
  Eventually I solved things by throwing away blocking
  /dev/random  and replaced it with symlink to  /dev/urandom
  It isn't pretty, nor exactly kosher, but having services
  hung is worse, than slight weakening of randomness.
Comment 1 Joe Orton 2003-08-29 10:29:28 EDT
Yes, we're switching to use /dev/urandom, there's no real need to have strong
random bits for what httpd does with them.
Comment 2 Joe Orton 2003-09-08 20:54:14 EDT
Fixed in apr-0.9.3-14.
Comment 3 Mark J. Cox (Product Security) 2003-12-16 16:45:21 EST
An errata has been issued which should help the problem described in this bug report. 
This report is therefore being closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files, please follow the link below. You may reopen 
this bug report if the solution does not work for you.

Comment 4 Steven Roberts 2005-02-23 23:47:00 EST
It looks like this fix is only working around a kernel issue where 
the entropy is never being replenished.  did any R&D happen on 
looking into that? 
Comment 5 Joe Orton 2005-02-24 02:20:03 EST
There were some known issues in earlier 2.4 kernels in the entropy
handling, which did get fixed, IIRC, but still, it's expected
behaviour that a read() on /dev/random may block for "a long time".
Comment 6 Steven Roberts 2005-02-24 02:29:39 EST
you don't happen to know what patchlevels in the 2.4 series had the 
problem do you?  we have a box running 2.4.20+RH patches that has an 
entropy of 0 (which thus hung httpd on restart), and has been that 
way for over a day.  I symlink'd /dev/random to /dev/urandom for now. 
Comment 7 Joe Orton 2005-02-24 03:53:50 EST
It affected the 2.4.21-based RHEL3 kernel; bug 117218 tracked it.

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