pack: upcast to size_t for bounds checking

Author: ethomson

src/libgit2/pack.c

@@ -1499,6 +1499,7 @@ static int pack_entry_find_offset(
 	size_t len)
 {
 	const uint32_t *level1_ofs;
+	size_t ofs_delta = 0;
 	const unsigned char *index;
 	unsigned hi, lo, stride;
 	int pos, found = 0;
@@ -1524,13 +1525,11 @@ static int pack_entry_find_offset(
 
 	if (p->index_version > 1) {
 		level1_ofs += 2;
+		ofs_delta = 2;
 		index += 8;
+	}
 
-		if ((int)short_oid->id[0] + 2 >= p->index_map.len) {
-			git_error_set(GIT_ERROR_INTERNAL, "internal error: p->short_oid->[0] out of bounds");
-			goto cleanup;
-		}
-	} else if ((int)short_oid->id[0] >= p->index_map.len) {
+	if ((size_t)short_oid->id[0] + ofs_delta >= p->index_map.len) {
 		git_error_set(GIT_ERROR_INTERNAL, "internal error: p->short_oid->[0] out of bounds");
 		goto cleanup;
 	}