From: Jiri Pirko <jiri@resnulli.us>
To: Michal Kubecek <mkubecek@suse.cz>
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 11:30:15 +0200 [thread overview]
Message-ID: <20191010093015.GF2223@nanopsycho> (raw)
In-Reply-To: <20191010091347.GA22163@unicorn.suse.cz>
Thu, Oct 10, 2019 at 11:13:47AM CEST, mkubecek@suse.cz wrote:
>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.
Ah, I missed that. Thanks!
>
>Michal
next prev parent reply other threads:[~2019-10-10 9:30 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
2019-10-10 9:30 ` Jiri Pirko [this message]
2019-10-10 9:31 ` Jiri Pirko
2019-10-10 10:45 ` Michal Kubecek
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