[Bug 938078] [NEW] Problems with mod_rewrite since updating to 2.2.14-5ubuntu8.8

[Howard Davis]

Public bug reported:

We have been having intermittent problems with incorrect URLs being
generated on some of our web pages since upgrading to the apache2
version 2.2.14-5ubuntu8.8

The problems seem to occur during periods where the site has higher
traffic levels.  The URLs are being generated by the CakePHP route
module which uses mod_rewrite.  The generated URLs appear to have text
from several different unrelated URLs all mixed together.  For example
when the generated URL should have been:

http://amblingbooks.com/books/category/fiction/adventure

The generated URL instead ended up as

http://amblingbooks.com/index.php/Pira/books/view/media/media/image
/4c9ae47d-b3cc-
4a21-8668-76b51b6b93e0/resize:width|71;height|130/books/view/books/view/media/media/image/4c9aed09-69c0-4e86
-882f-
327c1b6b93e0/resize:width|71;height|130/books/view/books/category/non_fiction/books/view/media/media/image
/4f21e8cc-62cc-4a81-9bfd-
67a41b6b93e0/resize:width|71;height|130/media/media/image/4ce1cc94-fc74-48c2-a363-6bb61b6b93e0/resize:width|71;height|130/media/media/image
/4f3b130b-
903c-4476-a765-3bca1b6b93e0/resize:width|71;height|130/media/media/image/4f21e8b2-3ee4-42b4
-b69d-
67a41b6b93e0/resize:width|71;height|130/media/media/image/4c9ae4b1-f9d4-4722
-ae0b-
76b51b6b93e0/resize:width|71;height|130/media/media/image/4efa257d-8114-4c09-8752-23b8c0a89265/resize:width|71;height|130/media/media/image
/4c9ae47d-b3cc-
4a21-8668-76b51b6b93e0/resize:width|71;height|130/media/media/image
/4c9aef7b-401c-
42d9-ae34-327c1b6b93e0/resize:width|71;height|130/books/index/books/view/media/media/image/4c9ae5ab-e330-4b30-96b7-76b51b6b93e0/resize:width|71;height|130/books/view/media/media/image/4f184db8-ff48
-494c-a95b-7feec0a89265/resize:width|71;height|130/adventure

which somehow has text from several other URLs mixed into it.

We have been tracking this problem for several days now.  We are seeing
the problem intermittently, sometimes the URLs generate correctly and
other times they do not.  Our investigation so far is suggesting that
these problems started happening when we picked up the upgrade to
apache2 version 2.2.14-5ubuntu8.8 which includes a change in the
mod_rewrite logic.

Is it possible that the recent mod_rewrite change has introduced an
issue with a buffer not being initialized properly and using old
incorrect data from the uninitialized buffer when generating the URL, or
introduced an SMP window where during heavy traffic levels with multiple
threads concurrently executing the mod_rewrite logic it somehow allows
incorrect URLs to be generated?

Our server is running Ubuntu 10.04.4 LTS

** Affects: apache2 (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/938078

Title:
  Problems with mod_rewrite since updating to 2.2.14-5ubuntu8.8

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