Bug 18986 (CVE-2009-5155)

Summary: ERE '0|()0|\1|0' causes regexec undefined behavior
Product: glibc Reporter: Paul Eggert <eggert>
Component: regexAssignee: Adhemerval Zanella <adhemerval.zanella>
Status: RESOLVED FIXED    
Severity: normal CC: adhemerval.zanella, arekm, drepper.fsp, fweimer, hanno
Priority: P2 Flags: eggert: security+
Version: 2.22   
Target Milestone: 2.28   
Host: Target:
Build: Last reconfirmed:
Attachments: Test program illustrating the bug.

Description Paul Eggert 2015-09-20 02:10:42 UTC
Created attachment 8621 [details]
Test program illustrating the bug.

This bug report was inspired by an assertion failure in GNU grep:

http://bugs.gnu.org/21513

I tracked it down to undefined behavior in glibc.  Sometimes the behavior causes a core dump, sometimes the wrong answer, sometimes the right answer.  I will attach a C program that illustrates the problem for me: compile and run it, and typically it outputs "match (incorrect)"; it should output either ""regcomp returns REG_ESUBREG (arguably correct)" or "no match (arguably correct)".

I have fixed the bug in the Gnulib version of the regex code, here:

http://git.savannah.gnu.org/cgit/gnulib.git/commit/?id=5513b40999149090987a0341c018d05d3eea1272

so when somebody backports Gnulib fixes into Glibc, Glibc should pick up the bug fix as a part of that process.
Comment 1 cvs-commit@gcc.gnu.org 2018-07-04 12:56:25 UTC
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- Log -----------------------------------------------------------------
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=eb04c21373e2a2885f3d52ff192b0499afe3c672

commit eb04c21373e2a2885f3d52ff192b0499afe3c672
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Wed Dec 20 09:47:44 2017 -0200

    posix: Sync gnulib regex implementation
    
    This patch syncs the regex implementation with gnulib (commit 0ee5212).
    Only two changes in GLIBC regex testing are required:
    
      1. posix/bug-regex28.c: as previously discussed [1] the change of
         expected results on the pattern should be safe.
    
      2. posix/PCRE.tests: the ERE (a)|\1 is malformed (in the sense that
         the \1 doesn't mean anything) and although current GLIBC accepts
         it has undefined behavior.  This patch removes the specific test.
    
    This sync contains some patches from thread 'Regex: Make libc regex
    more usable outside GLIBC.' [2] which have been pushed upstream in
    gnulib.  This patches also fixes some regex issues (BZ #23233,
    BZ #21163, BZ #18986, BZ #13762) and I did not add testcases for
    both #23233 and #13762 because I couldn't think a simple way to
    trigger the expected failure path to trigger them.
    
    Checked on x86_64-linux-gnu and i686-linux-gnu.
    
    	[BZ #23233]
    	[BZ #21163]
    	[BZ #18986]
    	[BZ #13762]
    	* posix/Makefile (tests): Add bug-regex37 and bug-regex38.
    	* posix/PCRE.tests: Remove invalid test.
    	* posix/bug-regex28.c: Fix expected values for used syntax.
    	* posix/bug-regex37.c: New file.
    	* posix/bug-regex38.c: Likewise.
    	* posix/regcomp.c: Sync with gnulib.
    	* posix/regex.c: Likewise.
    	* posix/regex.h: Likewise.
    	* posix/regex_internal.c: Likewise.
    	* posix/regex_internal.h: Likewise.
    	* posix/regexec.c: Likewise.
    
    [1] https://sourceware.org/ml/libc-alpha/2017-12/msg00807.html
    [2] https://sourceware.org/ml/libc-alpha/2017-12/msg00237.html

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                                       |   18 +
 posix/Makefile                                  |    3 +-
 posix/PCRE.tests                                |   13 -
 posix/bug-regex28.c                             |   46 +-
 wcsmbs/test-char-types.c => posix/bug-regex37.c |   11 +-
 wcsmbs/test-char-types.c => posix/bug-regex38.c |   11 +-
 posix/regcomp.c                                 |  597 +++++++++------
 posix/regex.c                                   |   21 +-
 posix/regex.h                                   |  335 +++++----
 posix/regex_internal.c                          |  295 ++++----
 posix/regex_internal.h                          |  442 ++++++++----
 posix/regexec.c                                 |  936 ++++++++++++-----------
 12 files changed, 1557 insertions(+), 1171 deletions(-)
 copy wcsmbs/test-char-types.c => posix/bug-regex37.c (78%)
 copy wcsmbs/test-char-types.c => posix/bug-regex38.c (78%)
Comment 2 Adhemerval Zanella 2018-07-04 12:59:58 UTC
Fixed by eb04c21373e2a2885f3d52ff192b0499afe3c672 (2.28).