Messages in this thread | | | Date | Thu, 10 Oct 2019 11:13:47 +0200 | From | Michal Kubecek <> | Subject | Re: [PATCH net-next] genetlink: do not parse attributes for families with zero maxattr |
| |
On Thu, Oct 10, 2019 at 10:39:58AM +0200, Jiri Pirko wrote: > Wed, Oct 09, 2019 at 06:44:32PM CEST, mkubecek@suse.cz wrote: > >Commit c10e6cf85e7d ("net: genetlink: push attrbuf allocation and parsing > >to a separate function") moved attribute buffer allocation and attribute > >parsing from genl_family_rcv_msg_doit() into a separate function > >genl_family_rcv_msg_attrs_parse() which, unlike the previous code, calls > >__nlmsg_parse() even if family->maxattr is 0 (i.e. the family does its own > >parsing). The parser error is ignored and does not propagate out of > >genl_family_rcv_msg_attrs_parse() but an error message ("Unknown attribute > >type") is set in extack and if further processing generates no error or > >warning, it stays there and is interpreted as a warning by userspace. > > > >Dumpit requests are not affected as genl_family_rcv_msg_dumpit() bypasses > >the call of genl_family_rcv_msg_doit() if family->maxattr is zero. Do the > >same also in genl_family_rcv_msg_doit(). > > This is the original code before the changes: > > if (ops->doit == NULL) > return -EOPNOTSUPP; > > if (family->maxattr && family->parallel_ops) { > attrbuf = kmalloc_array(family->maxattr + 1, > sizeof(struct nlattr *), > GFP_KERNEL); > if (attrbuf == NULL) > return -ENOMEM; > } else > attrbuf = family->attrbuf; > > if (attrbuf) { > enum netlink_validation validate = NL_VALIDATE_STRICT; > > if (ops->validate & GENL_DONT_VALIDATE_STRICT) > validate = NL_VALIDATE_LIBERAL; > > err = __nlmsg_parse(nlh, hdrlen, attrbuf, family->maxattr, > family->policy, validate, extack); > if (err < 0) > goto out; > } > > Looks like the __nlmsg_parse() is called no matter if maxattr if 0 or > not. It is only considered for allocation of attrbuf. This is in-sync > with the current code.
If family->maxattr is 0, genl_register_family() sets family->attrbuf to NULL so that attrbuf is also NULL and the whole "if (attrbuf) { ... }" block is not executed.
Michal
| |