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Date:   Fri, 17 Jul 2020 23:17:04 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>, davem@...emloft.net
Cc:     Jakub Kicinski <kuba@...nel.org>, Jiri Pirko <jiri@...lanox.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Michal Kubecek <mkubecek@...e.cz>,
        "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net: genetlink: Move initialization to core_initcall

Hi

On 15.07.2020 09:41, Daniel Lezcano wrote:
> The generic netlink is initialized far after the netlink protocol
> itself at subsys_initcall. The devlink is initialized at the same
> level, but after, as shown by a disassembly of the vmlinux:
>
> [ ... ]
> 374 ffff8000115f22c0 <__initcall_devlink_init4>:
> 375 ffff8000115f22c4 <__initcall_genl_init4>:
> [ ... ]
>
> The function devlink_init() calls genl_register_family() before the
> generic netlink subsystem is initialized.
>
> As the generic netlink initcall level is set since 2005, it seems that
> was not a problem, but now we have the thermal framework initialized
> at the core_initcall level which creates the generic netlink family
> and sends a notification which leads to a subtle memory corruption
> only detectable when the CONFIG_INIT_ON_ALLOC_DEFAULT_ON option is set
> with the earlycon at init time.
>
> The thermal framework needs to be initialized early in order to begin
> the mitigation as soon as possible. Moving it to postcore_initcall is
> acceptable.
>
> This patch changes the initialization level for the generic netlink
> family to the core_initcall and comes after the netlink protocol
> initialization.
>
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>

I confirm, that this change together with the thermal subsystem initcall 
change fixes the issue observed in linux-next for the last few days.

Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>

> ---
>   net/netlink/genetlink.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
> index 55ee680e9db1..36b8a1909826 100644
> --- a/net/netlink/genetlink.c
> +++ b/net/netlink/genetlink.c
> @@ -1263,7 +1263,7 @@ static int __init genl_init(void)
>   	panic("GENL: Cannot register controller: %d\n", err);
>   }
>   
> -subsys_initcall(genl_init);
> +core_initcall(genl_init);
>   
>   static int genlmsg_mcast(struct sk_buff *skb, u32 portid, unsigned long group,
>   			 gfp_t flags)

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

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