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Fix oss-fuzz issue 781: read from bad memory when fewer capturing parens than 

space in the external ovector.
This commit is contained in:
Philip.Hazel 2017-03-10 15:53:49 +00:00
parent 69fee50e5f
commit 143c136ac6
2 changed files with 16 additions and 4 deletions
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14
ChangeLog
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@ -14,10 +14,20 @@ hard-to-do issues such as #1887 in Bugzilla. The code is also cleaner because
the old code had a number of fudges to try to reduce stack usage. It seems to the old code had a number of fudges to try to reduce stack usage. It seems to
run no slower than the old code. run no slower than the old code.
A number of bugs in the refactored code were subsequently fixed during testing
before release, but after the code was made available in the repository. Many
of the bugs were discovered by fuzzing testing. These bugs were never in fully
released code, but are noted here for the record.
(a) If a pattern had fewer capturing parentheses than the ovector supplied in
the match data block, a memory error (detectable by ASAN) occurred after
a match, because the external block was being set from non-existent
internal ovector fields. Fixes oss-fuzz issue 781.
2. Hardened pcre2test so as to reduce the number of bugs reported by fuzzers: 2. Hardened pcre2test so as to reduce the number of bugs reported by fuzzers:
(a) Check for malloc failures when getting memory for the ovector (POSIX) or (a) Check for malloc failures when getting memory for the ovector (POSIX) or
the match data block (non-POSIX). the match data block (non-POSIX).
3. In the 32-bit library in non-UTF mode, an attempt to find a Unicode property 3. In the 32-bit library in non-UTF mode, an attempt to find a Unicode property
for a character with a code point greater than 0x10ffff (the Unicode maximum) for a character with a code point greater than 0x10ffff (the Unicode maximum)

6
src/pcre2_match.c
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@ -816,9 +816,11 @@ fprintf(stderr, "++ op=%d\n", *Fecode);
ovector[0] = Fstart_match - mb->start_subject; ovector[0] = Fstart_match - mb->start_subject;
ovector[1] = Feptr - mb->start_subject; ovector[1] = Feptr - mb->start_subject;
memcpy(ovector+2, Fovector, (oveccount - 1) * 2 * sizeof(PCRE2_SIZE));
/* Set i to the smaller of the sizes of the external and frame ovectors. */
i = 2 * ((top_bracket + 1 > oveccount)? oveccount : top_bracket + 1); i = 2 * ((top_bracket + 1 > oveccount)? oveccount : top_bracket + 1);
memcpy(ovector + 2, Fovector, (i - 2) * sizeof(PCRE2_SIZE));
while (--i >= Foffset_top + 2) ovector[i] = PCRE2_UNSET; while (--i >= Foffset_top + 2) ovector[i] = PCRE2_UNSET;
return MATCH_MATCH; /* Note: NOT RRETURN */ return MATCH_MATCH; /* Note: NOT RRETURN */