netdev - Re: [PATCH v2 net 13/17] net: Fix data-races around sysctl_fb_tunnels_only_for_init

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Date:   Thu, 18 Aug 2022 09:17:04 -0700
From:   Kuniyuki Iwashima <kuniyu@...zon.com>
To:     <kuniyu@...zon.com>
CC:     <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
        <kuni1840@...il.com>, <netdev@...r.kernel.org>, <pabeni@...hat.com>
Subject: Re: [PATCH v2 net 13/17] net: Fix data-races around sysctl_fb_tunnels_only_for_init_net.

From:   Kuniyuki Iwashima <kuniyu@...zon.com>
Date:   Wed, 17 Aug 2022 20:52:23 -0700
> While reading sysctl_fb_tunnels_only_for_init_net, it can be changed
> concurrently.  Thus, we need to add READ_ONCE() to its readers.
> 
> Fixes: 79134e6ce2c9 ("net: do not create fallback tunnels for non-default namespaces")
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
> ---
>  include/linux/netdevice.h | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 1a3cb93c3dcc..89a9545d90db 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -640,9 +640,11 @@ extern int sysctl_devconf_inherit_init_net;
>   */
>  static inline bool net_has_fallback_tunnels(const struct net *net)
>  {
> +	int fb_tunnels_only_for_init_net = READ_ONCE(sysctl_fb_tunnels_only_for_init_net);
> +

This should be in the #if IS_ENABLED(CONFIG_SYSCTL) block...my bad.
I'll fix this in v3.


>  	return !IS_ENABLED(CONFIG_SYSCTL) ||
> -	       !sysctl_fb_tunnels_only_for_init_net ||
> -	       (net == &init_net && sysctl_fb_tunnels_only_for_init_net == 1);
> +	       !fb_tunnels_only_for_init_net ||
> +	       (net == &init_net && fb_tunnels_only_for_init_net == 1);
>  }
>  
>  static inline int netdev_queue_numa_node_read(const struct netdev_queue *q)
> -- 
> 2.30.2