Bug 1165626

The is a bug in the PCRE library as reported to upstream <http://bugs.exim.org/show_bug.cgi?id=1546>:

echo "a" | /tmp/pcre-8.36/pcregrep "((?=(?(?=(?(?=(?(?=())))*))))){2}" -
=================================================================
==29857==ERROR: AddressSanitizer: heap-buffer-overflow on address
0x61000000fb94 at pc 0x7faf416f0dc6 bp 0x7fff9c91d3b0 sp 0x7fff9c91d3a8
READ of size 1 at 0x61000000fb94 thread T0
    #0 0x7faf416f0dc5 in match /tmp/pcre-8.36/pcre_exec.c:1410:9
    #1 0x7faf416dfe35 in match /tmp/pcre-8.36/pcre_exec.c:1538:7
    #2 0x7faf416e46de in match /tmp/pcre-8.36/pcre_exec.c:1399:7
    #3 0x7faf416dfe35 in match /tmp/pcre-8.36/pcre_exec.c:1538:7
    #4 0x7faf416ee260 in match /tmp/pcre-8.36/pcre_exec.c:983:9
    #5 0x7faf416dcd49 in pcre_exec /tmp/pcre-8.36/pcre_exec.c:6923:8
    #6 0x4a4580 in match_patterns /tmp/pcre-8.36/pcregrep.c:1449:10
    #7 0x4a13ca in pcregrep /tmp/pcre-8.36/pcregrep.c:1679:11
    #8 0x4a3624 in grep_or_recurse /tmp/pcre-8.36/pcregrep.c:2122:10
    #9 0x49efbf in main /tmp/pcre-8.36/pcregrep.c:3251:13
    #10 0x7faf405b7ec4 in __libc_start_main
/build/buildd/eglibc-2.19/csu/libc-start.c:287
    #11 0x4172a6 in _start (/tmp/pcre-8.36/.libs/lt-pcregrep+0x4172a6)

Upstream prepared a fix:

--- pcre_exec.c (revision 1512)
+++ pcre_exec.c (working copy)
@@ -1404,8 +1404,11 @@
         condition = TRUE;

         /* Advance ecode past the assertion to the start of the first branch,
-        but adjust it so that the general choosing code below works. */
-
+        but adjust it so that the general choosing code below works. If the 
+        assertion has a quantifier that allows zero repeats we must skip over 
+        the BRAZERO. This is a lunatic thing to do, but somebody did! */
+        
+        if (*ecode == OP_BRAZERO) ecode++; 
         ecode += GET(ecode, 1);
         while (*ecode == OP_ALT) ecode += GET(ecode, 1);
         ecode += 1 + LINK_SIZE - PRIV(OP_lengths)[condcode];

Which has not yet been pushed into the repository. Unfortunately, I cannot reproduce the bug.

The patch will be applied after it emerges in the repository.