netdev - Re: [PATCH 3/7] netlink: set extack error message in nla

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Message-ID: <3e7aadff-5228-660a-537a-9b54c11fa5cc@gmail.com>
Date:   Wed, 19 Sep 2018 09:20:19 -0700
From:   David Ahern <dsahern@...il.com>
To:     Johannes Berg <johannes@...solutions.net>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Cc:     Johannes Berg <johannes.berg@...el.com>
Subject: Re: [PATCH 3/7] netlink: set extack error message in nla_validate()

On 9/19/18 5:08 AM, Johannes Berg wrote:
> From: Johannes Berg <johannes.berg@...el.com>
> 
> In nla_parse() we already set this, but it makes sense to
> also do it in nla_validate() which already also sets the
> bad attribute pointer.
> 
> CC: David Ahern <dsahern@...il.com>
> Signed-off-by: Johannes Berg <johannes.berg@...el.com>
> ---
>  lib/nlattr.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/nlattr.c b/lib/nlattr.c
> index e2e5b38394d5..33404745bec4 100644
> --- a/lib/nlattr.c
> +++ b/lib/nlattr.c
> @@ -180,9 +180,13 @@ int nla_validate(const struct nlattr *head, int len, int maxtype,
>  	int rem;
>  
>  	nla_for_each_attr(nla, head, len, rem) {
> -		int err = validate_nla(nla, maxtype, policy, NULL);
> +		static const char _msg[] = "Attribute failed policy validation";
> +		const char *msg = _msg;
> +		int err = validate_nla(nla, maxtype, policy, &msg);
>  
>  		if (err < 0) {
> +			if (extack)
> +				extack->_msg = msg;
>  			NL_SET_BAD_ATTR(extack, nla);

msg, NL_SET_BAD_ATTR and extack handling all can be done in validate_nla
removing the need for the same message ("Attribute failed policy
validation") to be declared twice and simplifying the extack setting.

>  			return err;
>  		}
>