Re: [PATCH] cfg80211: use parallel_ops for genl

[Denis Kenzior <denkenz@xxxxxxxxx>]

Hi Johannes,

On 7/26/19 2:16 PM, Johannes Berg wrote:
> From: Johannes Berg <johannes.berg@xxxxxxxxx>
>
> Over time, we really need to get rid of all of our global locking.
> One of the things needed is to use parallel_ops. This isn't really
> the most important (RTNL is much more important) but OTOH we just
> keep adding uses of genl_family_attrbuf() now. Use .parallel_ops to
> disallow this.
>
> Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
> ---
>   net/wireless/nl80211.c | 112 +++++++++++++++++++++++++++++------------
>   1 file changed, 81 insertions(+), 31 deletions(-)
>
> diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
> index 10b57aa10227..59aefcd7ccb6 100644
> --- a/net/wireless/nl80211.c
> +++ b/net/wireless/nl80211.c
> @@ -749,19 +749,29 @@ int nl80211_prepare_wdev_dump(struct netlink_callback *cb,
>   	int err;
>   
>   	if (!cb->args[0]) {
> +		struct nlattr **attrbuf;
> +
> +		attrbuf = kcalloc(NUM_NL80211_ATTR, sizeof(*attrbuf),
> +				  GFP_KERNEL);
> +		if (!attrbuf)
> +			return -ENOMEM;
> +
>   		err = nlmsg_parse_deprecated(cb->nlh,
>   					     GENL_HDRLEN + nl80211_fam.hdrsize,
> -					     genl_family_attrbuf(&nl80211_fam),
> -					     nl80211_fam.maxattr,
> +					     attrbuf, nl80211_fam.maxattr,
>   					     nl80211_policy, NULL);
> -		if (err)
> +		if (err) {
> +			kfree(attrbuf);
>   			return err;
> +		}
>   
> -		*wdev = __cfg80211_wdev_from_attrs(
> -					sock_net(cb->skb->sk),
> -					genl_family_attrbuf(&nl80211_fam));
> -		if (IS_ERR(*wdev))
> +		*wdev = __cfg80211_wdev_from_attrs(sock_net(cb->skb->sk),
> +						   attrbuf);
> +		kfree(attrbuf);
> +		if (IS_ERR(*wdev)) {
> +			kfree(attrbuf);

Hmm, you just freed attrbuf above?

>   			return PTR_ERR(*wdev);
> +		}
>   		*rdev = wiphy_to_rdev((*wdev)->wiphy);
>   		/* 0 is the first index - add 1 to parse only once */
>   		cb->args[0] = (*rdev)->wiphy_idx + 1;

<snip>

> @@ -12846,24 +12880,32 @@ static int nl80211_prepare_vendor_dump(struct sk_buff *skb,
>   		return 0;
>   	}
>   
> +	attrbuf = kcalloc(NUM_NL80211_ATTR, sizeof(*attrbuf), GFP_KERNEL);
> +	if (!attrbuf)
> +		return -ENOMEM;
> +
>   	err = nlmsg_parse_deprecated(cb->nlh,
>   				     GENL_HDRLEN + nl80211_fam.hdrsize,
>   				     attrbuf, nl80211_fam.maxattr,
>   				     nl80211_policy, NULL);
>   	if (err)
> -		return err;
> +		goto out;
>   
>   	if (!attrbuf[NL80211_ATTR_VENDOR_ID] ||
> -	    !attrbuf[NL80211_ATTR_VENDOR_SUBCMD])
> -		return -EINVAL;
> +	    !attrbuf[NL80211_ATTR_VENDOR_SUBCMD]) {
> +		err = -EINVAL;
> +		goto out;
> +	}

Might be nicer to just set err = -EINVAL before the if instead of using 
{} here

>   
>   	*wdev = __cfg80211_wdev_from_attrs(sock_net(skb->sk), attrbuf);
>   	if (IS_ERR(*wdev))
>   		*wdev = NULL;
>   
>   	*rdev = __cfg80211_rdev_from_attrs(sock_net(skb->sk), attrbuf);
> -	if (IS_ERR(*rdev))
> -		return PTR_ERR(*rdev);
> +	if (IS_ERR(*rdev)) {
> +		err = PTR_ERR(*rdev);
> +		goto out;
> +	}
>   
>   	vid = nla_get_u32(attrbuf[NL80211_ATTR_VENDOR_ID]);
>   	subcmd = nla_get_u32(attrbuf[NL80211_ATTR_VENDOR_SUBCMD]);
> @@ -12876,15 +12918,19 @@ static int nl80211_prepare_vendor_dump(struct sk_buff *skb,
>   		if (vcmd->info.vendor_id != vid || vcmd->info.subcmd != subcmd)
>   			continue;
>   
> -		if (!vcmd->dumpit)
> -			return -EOPNOTSUPP;
> +		if (!vcmd->dumpit) {
> +			err = -EOPNOTSUPP;
> +			goto out;
> +		}

Same thing here, setting err = -EOPNOTSUPP before the for...

>   
>   		vcmd_idx = i;
>   		break;
>   	}
>   
> -	if (vcmd_idx < 0)
> -		return -EOPNOTSUPP;
> +	if (vcmd_idx < 0) {
> +		err = -EOPNOTSUPP;
> +		goto out;
> +	}
>   
>   	if (attrbuf[NL80211_ATTR_VENDOR_DATA]) {
>   		data = nla_data(attrbuf[NL80211_ATTR_VENDOR_DATA]);

<snip>

Otherwise LGTM.

Feel free to add: Reviewed-by: Denis Kenzior <denkenz@xxxxxxxxx>

Regards,
-Denis