Fix parser out-of-bounds reads - #131
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dag-erling
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Jan 31, 2026
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ping @laurikari |
By passing exact-length unpadded inputs to regncomp, we can catch out-of-bounds reads using -fsanitize=address.
Many tools expect source files to have some valid encoding (like UTF-8), this makes them happy.
These were all found with the latest retest.c using the Address Sanitizer with: CFLAGS=-O1 -g -fsanitize=address -fno-omit-frame-pointer LDFLAGS=-fsanitize=address
dag-erling
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May 15, 2026
| buf = xmalloc(len * sizeof(CHAR_T)); | ||
| if (buf == NULL) | ||
| return REG_ESPACE; | ||
| memcpy(buf, data, len * sizeof(CHAR_T)); |
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This is likely to still be null-terminated at least some of the time. It would be better to allocate a slightly larger buffer and deliberately set the first out-of-bounds character to something non-zero.
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static int
wrap_regcomp(regex_t *preg, const CHAR_T *data, size_t len, int cflags)
{
#ifdef HAVE_REGNCOMP
CHAR_T *buf;
int ret;
if (use_regncomp)
{
buf = xmalloc((len + 1) * sizeof(CHAR_T));
if (buf == NULL)
return REG_ESPACE;
memcpy(buf, data, len * sizeof(CHAR_T));
buf[len] = (CHAR_T)~0;
ret = tre_regncomp(preg, buf, len, cflags);
xfree(buf);
return ret;
}
#endif /* HAVE_REGNCOMP */
return tre_regcomp(preg, data, cflags);
}
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Updated
retestsoregncompis called with a strictly non‑padded input buffer, rather than passing aNULterminated buffer. With that in place, AddressSanitizer exposed several out‑of‑bounds reads in the parser.Added a few additional parser test cases around atoms, bracket expressions, and escapes.
Then fixed the parser, adding explicit bounds checks and better error handling.