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>
---
Makefile | 3 ++-
git-compat-util.h | 13 +++++++++++++
2 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/Makefile b/Makefile
index df4f86b..c6f7f66 100644
--- a/Makefile
+++ b/Makefile
@@ -301,7 +301,8 @@ all::
# crashes due to allocation and free working on different 'heaps'.
# It's defined automatically if USE_NED_ALLOCATOR is set.
#
-# Define NO_REGEX if you have no or inferior regex support in your C library.
+# Define NO_REGEX if your C library lacks regex support with REG_STARTEND
+# feature.
#
# Define HAVE_DEV_TTY if your system can open /dev/tty to interact with the
# user.
diff --git a/git-compat-util.h b/git-compat-util.h
index 37cce07..8aab0c3 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -977,6 +977,19 @@ void git_qsort(void *base, size_t nmemb, size_t size,
#define qsort git_qsort
#endif
+#ifndef REG_STARTEND
+#error "Git requires REG_STARTEND support. Compile with NO_REGEX=NeedsStartEnd"
+#endif
+
+static inline int regexec_buf(const regex_t *preg, const char *buf, size_t size,
+ size_t nmatch, regmatch_t pmatch[], int eflags)
+{
+ assert(nmatch > 0 && pmatch);
+ pmatch[0].rm_so = 0;
+ pmatch[0].rm_eo = size;
+ return regexec(preg, buf, nmatch, pmatch, eflags | REG_STARTEND);
+}
+
#ifndef DIR_HAS_BSD_GROUP_SEMANTICS
# define FORCE_DIR_SET_GID S_ISGID
#else
--
2.10.0.windows.1.10.g803177d