From: Michal Kubecek <mkubecek@suse.cz>
To: Jiri Pirko <jiri@resnulli.us>
Cc: "David S. Miller" <davem@davemloft.net>,
Jiri Pirko <jiri@mellanox.com>,
Johannes Berg <johannes@sipsolutions.net>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next] genetlink: do not parse attributes for families with zero maxattr
Date: Thu, 10 Oct 2019 11:13:47 +0200 [thread overview]
Message-ID: <20191010091347.GA22163@unicorn.suse.cz> (raw)
In-Reply-To: <20191010083958.GD2223@nanopsycho>
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
next prev parent reply other threads:[~2019-10-10 9:13 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-09 16:44 [PATCH net-next] genetlink: do not parse attributes for families with zero maxattr Michal Kubecek
2019-10-10 8:39 ` Jiri Pirko
2019-10-10 9:13 ` Michal Kubecek [this message]
2019-10-10 9:30 ` Jiri Pirko
2019-10-10 9:31 ` Jiri Pirko
2019-10-10 10:45 ` Michal Kubecek
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