netdev - Re: [PATCH] net: don't unnecessarily load kernel modules in dev

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Date:   Tue, 6 Mar 2018 15:59:20 -0800
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Paul Moore <pmoore@...hat.com>
Cc:     netdev@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>,
        Dominick Grift <dac.override@...il.com>, selinux@...ho.nsa.gov,
        linux-security-module@...r.kernel.org
Subject: Re: [PATCH] net: don't unnecessarily load kernel modules in
 dev_ioctl()

On Tue, 06 Mar 2018 17:27:44 -0500
Paul Moore <pmoore@...hat.com> wrote:

> From: Paul Moore <paul@...l-moore.com>
> 
> Starting with v4.16-rc1 we've been seeing a higher than usual number
> of requests for the kernel to load networking modules, even on events
> which shouldn't trigger a module load (e.g. ioctl(TCGETS)).  Stephen
> Smalley suggested the problem may lie in commit 44c02a2c3dc5
> ("dev_ioctl(): move copyin/copyout to callers") which moves changes
> the network dev_ioctl() function to always call dev_load(),
> regardless of the requested ioctl.
> 
> This patch moves the dev_load() calls back into the individual ioctls
> while preserving the rest of the original patch.
> 
> Reported-by: Dominick Grift <dac.override@...il.com>
> Suggested-by: Stephen Smalley <sds@...ho.nsa.gov>
> Signed-off-by: Paul Moore <paul@...l-moore.com>
> ---
>  net/core/dev_ioctl.c |    7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
> index 0ab1af04296c..a04e1e88bf3a 100644
> --- a/net/core/dev_ioctl.c
> +++ b/net/core/dev_ioctl.c
> @@ -402,8 +402,6 @@ int dev_ioctl(struct net *net, unsigned int cmd, struct ifreq *ifr, bool *need_c
>  	if (colon)
>  		*colon = 0;
>  
> -	dev_load(net, ifr->ifr_name);

Actually dev_load by ethernet name is really a legacy thing that should just die,

It was kept around so that some very tunnel configuration using special names.

	# ifconfig sit0

which probably several web pages still tell users to do...
We have much better control now with ip commands so that this is just
baggage.