[lvm-devel] [PATCH RFC] clvmd: verify messages before processing

[David Teigland]

On Wed, Jul 31, 2013 at 09:33:23AM +0100, Christine Caulfield wrote:
> >@@ -2189,10 +2286,22 @@ error:
> >  void process_message(struct local_client *client, char *buf, int len,
> >  		     const char *csid)
> >  {
> >+	char nodename[max_cluster_member_name_len];
> >  	struct clvm_header *inheader;
> >+	int rv;
> >
> >  	inheader = (struct clvm_header *) buf;
> >  	ntoh_clvm(inheader);	/* Byteswap fields */
> >+
> >+	rv = verify_message(buf, len);
> >+	if (rv < 0) {
> >+		memset(nodename, 0, sizeof(nodename));
> >+		clops->name_from_csid(csid, nodename);
> >+		log_error("process_message from %s len %d bad verify\n", nodename, len);
> >+		dump_message(buf, len);
> 
> Here you will probably have to return an error to the calling clvmd
> or you will get delays when the caller times out. If that happens
> then the 'timed-out' message is less than helpful

The thinking behind no reply was that if a command sends a bogus message,
it doesn't deserve a reply, and even if it got one, may not handle it
properly anyway.  So, if we're dealing with a bogus non-message, I think
we're beyond the point where we can be helpful.  I'm mainly trying to just
protect clvmd from faulty commands.  But, I looked at how feasible it
would be, and I don't think it's worth the trouble -- we'd have to do the
whole add_to_lvmqueue() thing, etc.