netdev - Re: [PATCH v2 net] netlink: Relax attr validation for fixed length types

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Date:   Thu, 07 Dec 2017 14:01:35 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     dsahern@...il.com
Cc:     netdev@...r.kernel.org, johannes@...solutions.net
Subject: Re: [PATCH v2 net] netlink: Relax attr validation for fixed length
 types

From: David Ahern <dsahern@...il.com>
Date: Wed,  6 Dec 2017 20:09:12 -0800

> Commit 28033ae4e0f5 ("net: netlink: Update attr validation to require
> exact length for some types") requires attributes using types NLA_U* and
> NLA_S* to have an exact length. This change is exposing bugs in various
> userspace commands that are sending attributes with an invalid length
> (e.g., attribute has type NLA_U8 and userspace sends NLA_U32). While
> the commands are clearly broken and need to be fixed, users are arguing
> that the sudden change in enforcement is breaking older commands on
> newer kernels for use cases that otherwise "worked".
> 
> Relax the validation to print a warning mesage similar to what is done
> for messages containing extra bytes after parsing.
> 
> Fixes: 28033ae4e0f5 ("net: netlink: Update attr validation to require exact length for some types")
> Signed-off-by: David Ahern <dsahern@...il.com>
> Reviewed-by: Johannes Berg <johannes@...solutions.net>
> ---
> v2
> - updated the comment before nla_attr_len and removed the outdated
>   comment before use of nla_attr_len

Applied and queued up for -stable, thanks David.