netdev - Re: [PATCH v2 0/2] netlink: export policy on validation failures

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Message-ID: <20201007100658.26013c81@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 7 Oct 2020 10:06:58 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     netdev@...r.kernel.org, dsahern@...il.com
Subject: Re: [PATCH v2 0/2] netlink: export policy on validation failures

On Tue,  6 Oct 2020 20:15:53 +0200 Johannes Berg wrote:
> Export the policy used for attribute validation when it fails,
> so e.g. for an out-of-range attribute userspace immediately gets
> the valid ranges back.
> 
> v2 incorporates the suggestion from Jakub to have a function to
> estimate the size (netlink_policy_dump_attr_size_estimate()) and
> check that it does the right thing on the *normal* policy dumps,
> not (just) when calling it from the error scenario.
> 
> 
> Tested using nl80211/iw in a few scenarios, seems to work fine
> and return the policy back, e.g.
> 
> kernel reports: integer out of range
> policy: 04 00 0b 00 0c 00 04 00 01 00 00 00 00 00 00 00 
>         ^ padding
>                     ^ minimum allowed value
> policy: 04 00 0b 00 0c 00 05 00 ff ff ff ff 00 00 00 00 
>         ^ padding
>                     ^ maximum allowed value
> policy: 08 00 01 00 04 00 00 00 
>         ^ type 4 == U32
> 
> for an out-of-range case.

Too minor nits, with those addressed:

Reviewed-by: Jakub Kicinski <kuba@...nel.org>