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+++ This bug was initially created as a clone of Bug #730952 +++

The bug happens when a collating symbol exists in the current locale that is composed of the same character multiple times (e.g. aa in nb_NO locales).  Attachment 537445 [details] is a zip file with reproducers from Terje Braten.

In this case, you have something like this:

   %fourier-alt-itaalic -s -0.168exnansi
   0         1
   012345678901234^

with cur_idx pointing to the "a" at &mctx->input.mbs[15], which is also the last character (valid_len = 16).  Bytes after the first "a" are leftovers from previous matching attempts.

"aa" is a multicharacter collation element in the bokmal locale, so re_string_elem_size_at returns 2 and check_node_accept_bytes matches 2 bytes even though there is only one byte in the string.  clean_state_log_if_needed then accesses one item past the allocated memory.

I haven't tested the reproducer on RHEL5/6, but the out-of-bounds access is clear and the code has been mostly unchanged for years; attachment 537575 [details] should apply more or less to all even not-so-recent glibc versions.

No automated test went in upstream that I'm aware of.  In general, it looks like Andreas was very very lax in submitting regression tests upstream.

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No Documentation Needed

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-2012-0763.html