linux-kernel - Re: [PATCH net-next] tun: fix group permission check

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Message-ID: <6751d9e5254ac_119ae629486@willemb.c.googlers.com.notmuch>
Date: Thu, 05 Dec 2024 11:50:45 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Stas Sergeev <stsp2@...dex.ru>, 
 netdev@...r.kernel.org
Cc: Stas Sergeev <stsp2@...dex.ru>, 
 Willem de Bruijn <willemdebruijn.kernel@...il.com>, 
 Jason Wang <jasowang@...hat.com>, 
 Andrew Lunn <andrew+netdev@...n.ch>, 
 "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, 
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] tun: fix group permission check

Stas Sergeev wrote:
> Currently tun checks the group permission even if the user have matched.
> Besides going against the usual permission semantic, this has a
> very interesting implication: if the tun group is not among the
> supplementary groups of the tun user, then effectively no one can
> access the tun device. CAP_SYS_ADMIN still can, but its the same as
> not setting the tun ownership.
> 
> This patch relaxes the group checking so that either the user match
> or the group match is enough. This avoids the situation when no one
> can access the device even though the ownership is properly set.
> 
> Also I simplified the logic by removing the redundant inversions:
> tun_not_capable() --> !tun_capable()
> 
> Signed-off-by: Stas Sergeev <stsp2@...dex.ru>
> 
> CC: Willem de Bruijn <willemdebruijn.kernel@...il.com>
> CC: Jason Wang <jasowang@...hat.com>
> CC: Andrew Lunn <andrew+netdev@...n.ch>
> CC: "David S. Miller" <davem@...emloft.net>
> CC: Eric Dumazet <edumazet@...gle.com>
> CC: Jakub Kicinski <kuba@...nel.org>
> CC: Paolo Abeni <pabeni@...hat.com>
> CC: netdev@...r.kernel.org
> CC: linux-kernel@...r.kernel.org

Reviewed-by: Willem de Bruijn <willemb@...gle.com>

A lot more readable this way too.