[PATCH 3/3] pathspec: handle non-terminated strings with :(attr)

From: Jeff King <peff@peff.net>
Date: Nov 2, 2018, 05:23 UTC
Message-ID: <20181102052322.GC19234@sigill.intra.peff.net>
In-Reply-To: <20181102052239.GA19162@sigill.intra.peff.net>

The pathspec code always takes names to be matched as a name/namelen pair, but match_attrs() never looks at namelen, and just treats "name" like a NUL-terminated string, passing it to git_check_attr().

This usually works anyway. Every caller passes a NUL-terminated string, and in all but one the passed-in length is the same as the length of the string (the exception is dir_path_match(), which may pass a smaller length to drop a trailing slash). So we won't currently ever read random memory, and the one case I found actually happens to work correctly because the attr code can handle the trailing slash itself.

But it's still worth addressing, as the function interface implies that the name does not have to be NUL-terminated, making this an accident waiting to happen.

Since teaching git_check_attr() to take a ptr/len pair would be a big refactor, we'll just allocate a new string. We can do this only when necessary, which avoids paying the cost for most callers.

Signed-off-by: Jeff King <peff@peff.net>
---
 dir.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/dir.c b/dir.c
index 47c2fca8dc..ab6477d777 100644
--- a/dir.c
+++ b/dir.c
@@ -281,8 +281,15 @@ static int match_attrs(const struct index_state *istate,
 		       const struct pathspec_item *item)
 {
 	int i;
+	char *to_free = NULL;
+
+	if (name[namelen])
+		name = to_free = xmemdupz(name, namelen);
 
 	git_check_attr(istate, name, item->attr_check);
+
+	free(to_free);
+
 	for (i = 0; i < item->attr_match_nr; i++) {
 		const char *value;
 		int matched;

-- 
2.19.1.1336.g081079ac04