Re: [PATCH net-next] genetlink: do not parse attributes for families with zero maxattr
From: Jiri Pirko <jiri@resnulli.us>
Date: 2019-10-10 08:40:06
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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;
}
quoted hunk ↗ jump to hunk
Fixes: c10e6cf85e7d ("net: genetlink: push attrbuf allocation and parsing to a separate function") Signed-off-by: Michal Kubecek <redacted> --- 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