On Thu, 10 Oct 2019 12:34:02 +0200 (CEST), Michal Kubecek 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().
>
> Fixes: c10e6cf85e7d ("net: genetlink: push attrbuf allocation and parsing to
> a separate function")
> Signed-off-by: Michal Kubecek <mkube...@suse.cz>
> ---
> net/netlink/genetlink.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
> index ecc2bd3e73e4..1f14e55ad3ad 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:
The use of a goto statement as a replacement for an if is making me
uncomfortable.
Looks like both callers of genl_family_rcv_msg_attrs_parse() jump
around it if !family->maxattr and then check the result with IS_ERR().
Would it not make more sense to have genl_family_rcv_msg_attrs_parse()
return NULL if !family->maxattr?
Just wondering, if you guys prefer this version I can apply..
> info.snd_seq = nlh->nlmsg_seq;
> info.snd_portid = NETLINK_CB(skb).portid;
> info.nlhdr = nlh;
> @@ -676,8 +678,7 @@ static int genl_family_rcv_msg_doit(const struct
> genl_family *family,
> family->post_doit(ops, skb, &info);
>
> out:
> - genl_family_rcv_msg_attrs_free(family, attrbuf,
> - family->maxattr && family->parallel_ops);
> + genl_family_rcv_msg_attrs_free(family, attrbuf, family->parallel_ops);
>
> return err;
> }
