We just introduced a test that demonstrates that our sloppy use of
regexec() on a mmap()ed area can result in incorrect results or even
hard crashes.
So what we need to fix this is a function that calls regexec() on a
length-delimited, rather than a NUL-terminated, string.
Happily, there is an extension to regexec() introduced by the NetBSD
project and present in all major regex implementation including
Linux', MacOSX' and the one Git includes in compat/regex/: by using
the (non-POSIX) REG_STARTEND flag, it is possible to tell the
regexec() function that it should only look at the offsets between
pmatch[0].rm_so and pmatch[0].rm_eo.
That is exactly what we need.
Since support for REG_STARTEND is so widespread by now, let's just
introduce a helper function that uses it, and fall back to allocating
and constructing a NUL-terminated when REG_STARTEND is not available.
Signed-off-by: Johannes Schindelin <johannes.schindelin@xxxxxx>
---
git-compat-util.h | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/git-compat-util.h b/git-compat-util.h
index db89ba7..19128b3 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -965,6 +965,27 @@ void git_qsort(void *base, size_t nmemb, size_t size,
#define qsort git_qsort
#endif
+static inline int regexec_buf(const regex_t *preg, const char *buf, size_t size,
+ size_t nmatch, regmatch_t pmatch[], int eflags)
+{
+#ifdef REG_STARTEND
+ assert(nmatch > 0 && pmatch);
+ pmatch[0].rm_so = 0;
+ pmatch[0].rm_eo = size;
+ return regexec(preg, buf, nmatch, pmatch, eflags | REG_STARTEND);
+#else
+ char *buf2 = xmalloc(size + 1);
+ int ret;
+
+ memcpy(buf2, buf, size);
+ buf2[size] = '\0';
+ ret = regexec(preg, buf2, nmatch, pmatch, eflags);
+ free(buf2);
+
+ return ret;
+#endif
+}
+
#ifndef DIR_HAS_BSD_GROUP_SEMANTICS
# define FORCE_DIR_SET_GID S_ISGID
#else
--
2.10.0.windows.1.10.g803177d