[PATCH] link_alt_odb_entry: fix read over array bounds reported by valgrind

[Heiko Voigt <hvoigt@hvoigt.net>]

pfxlen can be longer than the path in objdir when relative_base contains
the path to gits object directory.

Signed-off-by: Heiko Voigt <hvoigt@hvoigt.net>
---
 sha1_file.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/sha1_file.c b/sha1_file.c
index 4ccaf7a..631d0dd 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -251,7 +251,7 @@ static int link_alt_odb_entry(const char * entry, int len, const char * relative
 	const char *objdir = get_object_directory();
 	struct alternate_object_database *ent;
 	struct alternate_object_database *alt;
-	int pfxlen, entlen;
+	int pfxlen, entlen, objdirlen;
 	struct strbuf pathbuf = STRBUF_INIT;
 
 	if (!is_absolute_path(entry) && relative_base) {
@@ -298,7 +298,8 @@ static int link_alt_odb_entry(const char * entry, int len, const char * relative
 			return -1;
 		}
 	}
-	if (!memcmp(ent->base, objdir, pfxlen)) {
+	objdirlen = strlen(objdir);
+	if (!memcmp(ent->base, objdir, pfxlen > objdirlen ? objdirlen : pfxlen)) {
 		free(ent);
 		return -1;
 	}
-- 
1.7.12.rc0.23.gc9a5ac4