refs: prevent accidental NULL dereference in write_pseudoref

Several of the refs functions take NULL to indicate that the ref is not to be updated. If refs_update_ref were called with a NULL new object ID, we could pass that NULL pointer to write_pseudoref, which would then segfault when it dereferenced it. Instead, simply return successfully, since if we don't want to update the pseudoref, there's nothing to do. Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>

brian m. carlson committed Oct 15, 2017 at 22:06 UTC 6ee18216d8d9ca8f76b01282b36bdf590a64d8fc
1 file changed +3
refs.c
+3
@@ -583,6 +583,9 @@ static int write_pseudoref(const char *pseudoref, const struct object_id *oid,
583 struct strbuf buf = STRBUF_INIT;
584 int ret = -1;
585
586 + if (!oid)
587 + return 0;
588 +
589 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
590
591 filename = git_path("%s", pseudoref);