Subject: Re: [PATCH v4 3/4] net/sched: Load modules via their alias

From: Simon Horman <[email-masked]>
Date: Tue, 23 Jan 2024 17:40:02 +0000

On Tue, Jan 23, 2024 at 02:52:41PM +0100, Michal Koutný wrote:
> The cls_,sch_,act_ modules may be loaded lazily during network
> configuration but without user's awareness and control.
> 
> Switch the lazy loading from canonical module names to a module alias.
> This allows finer control over lazy loading, the precedent from
> commit 7f78e0351394 ("fs: Limit sys_mount to only request filesystem
> modules.") explains it already:
> 
> 	Using aliases means user space can control the policy of which
> 	filesystem^W net/sched modules are auto-loaded by editing
> 	/etc/modprobe.d/*.conf with blacklist and alias directives.
> 	Allowing simple, safe, well understood work-arounds to known
> 	problematic software.
> 
> By default, nothing changes. However, if a specific module is
> blacklisted (its canonical name), it won't be modprobe'd when requested
> under its alias (i.e. kernel auto-loading). It would appear as if the
> given module was unknown.
> 
> The module can still be loaded under its canonical name, which is an
> explicit (privileged) user action.
> 
> Signed-off-by: Michal Koutný <[email-masked]>
> ---
>  net/sched/act_api.c | 2 +-
>  net/sched/cls_api.c | 2 +-
>  net/sched/sch_api.c | 4 ++--
>  3 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/net/sched/act_api.c b/net/sched/act_api.c
> index 3e30d7260493..60c0fadfac6d 100644
> --- a/net/sched/act_api.c
> +++ b/net/sched/act_api.c
> @@ -1363,7 +1363,7 @@ struct tc_action_ops *tc_action_load_ops(struct nlattr *nla, u32 flags,
>  
>  		if (rtnl_held)
>  			rtnl_unlock();
> -		request_module("act_%s", act_name);
> +		request_module(NET_ACT_ALIAS_PREFIX "%s", name);

Hi Michal,

name doesn't exist in this context, perhaps the line above should be:

		request_module(NET_ACT_ALIAS_PREFIX "%s", act_name);

>  		if (rtnl_held)
>  			rtnl_lock();
>  
> diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
> index 92a12e3d0fe6..b31b832598e7 100644
> --- a/net/sched/cls_api.c
> +++ b/net/sched/cls_api.c
> @@ -257,7 +257,7 @@ tcf_proto_lookup_ops(const char *kind, bool rtnl_held,
>  #ifdef CONFIG_MODULES
>  	if (rtnl_held)
>  		rtnl_unlock();
> -	request_module("cls_%s", kind);
> +	request_module(NET_CLS_ALIAS_PREFIX "%s", name);

Likewise, perhaps the line above should be:

	request_module(NET_CLS_ALIAS_PREFIX "%s", kind);

>  	if (rtnl_held)
>  		rtnl_lock();
>  	ops = __tcf_proto_lookup_ops(kind);

...

-- 
pw-bot: changes-requested