Wed, Oct 09, 2019 at 06:44:32PM CEST, [email protected] 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 <[email protected]>
>---
> 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
>
