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Miller" , Jiri Pirko , Johannes Berg , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next] genetlink: do not parse attributes for families with zero maxattr Message-ID: <20191010083958.GD2223@nanopsycho> References: <20191009164432.AD5D1E3785@unicorn.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191009164432.AD5D1E3785@unicorn.suse.cz> User-Agent: Mutt/1.11.4 (2019-03-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. For dumpit, the check was there: if (family->maxattr) { unsigned int validate = NL_VALIDATE_STRICT; if (ops->validate & GENL_DONT_VALIDATE_DUMP_STRICT) validate = NL_VALIDATE_LIBERAL; rc = __nla_validate(nlmsg_attrdata(nlh, hdrlen), nlmsg_attrlen(nlh, hdrlen), family->maxattr, family->policy, validate, extack); if (rc) return rc; } > >Fixes: c10e6cf85e7d ("net: genetlink: push attrbuf allocation and parsing to a separate function") >Signed-off-by: Michal Kubecek >--- > net/netlink/genetlink.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > >diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c >index ecc2bd3e73e4..c4bf8830eedf 100644 >--- a/net/netlink/genetlink.c >+++ b/net/netlink/genetlink.c >@@ -639,21 +639,23 @@ static int genl_family_rcv_msg_doit(const struct genl_family *family, > const struct genl_ops *ops, > int hdrlen, struct net *net) > { >- struct nlattr **attrbuf; >+ struct nlattr **attrbuf = NULL; > struct genl_info info; > int err; > > if (!ops->doit) > return -EOPNOTSUPP; > >+ if (!family->maxattr) >+ goto no_attrs; > attrbuf = genl_family_rcv_msg_attrs_parse(family, nlh, extack, > ops, hdrlen, > GENL_DONT_VALIDATE_STRICT, >- family->maxattr && > family->parallel_ops); > if (IS_ERR(attrbuf)) > return PTR_ERR(attrbuf); > >+no_attrs: > info.snd_seq = nlh->nlmsg_seq; > info.snd_portid = NETLINK_CB(skb).portid; > info.nlhdr = nlh; >-- >2.23.0 >