netdev - Re: [PATCH net 1/3] dpll: fix pin dump crash after module unbind

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Date: Wed, 8 Nov 2023 12:36:12 +0100
From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
To: Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>,
	<netdev@...r.kernel.org>
CC: <vadim.fedorenko@...ux.dev>, <jiri@...nulli.us>,
	<michal.michalik@...el.com>, <milena.olech@...el.com>, <pabeni@...hat.com>,
	<kuba@...nel.org>
Subject: Re: [PATCH net 1/3] dpll: fix pin dump crash after module unbind

On 11/8/23 11:32, Arkadiusz Kubalewski wrote:
> Disallow dump of unregistered parent pins, it is possible when parent
> pin and dpll device registerer kernel module instance unbinds, and
> other kernel module instances of the same dpll device have pins
> registered with the parent pin. The user can invoke a pin-dump but as
> the parent was unregistered, thus shall not be accessed by the
> userspace, prevent that by checking if parent pin is still registered.
> 
> Fixes: 9d71b54b65b1 ("dpll: netlink: Add DPLL framework base functions")
> Signed-off-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>
> ---
>   drivers/dpll/dpll_netlink.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/dpll/dpll_netlink.c b/drivers/dpll/dpll_netlink.c
> index a6dc3997bf5c..93fc6c4b8a78 100644
> --- a/drivers/dpll/dpll_netlink.c
> +++ b/drivers/dpll/dpll_netlink.c
> @@ -328,6 +328,13 @@ dpll_msg_add_pin_parents(struct sk_buff *msg, struct dpll_pin *pin,
>   		void *parent_priv;
>   
>   		ppin = ref->pin;
> +		/*
> +		 * dump parent only if it is registered, thus prevent crash on
> +		 * pin dump called when driver which registered the pin unbinds
> +		 * and different instance registered pin on that parent pin
> +		 */
> +		if (!xa_get_mark(&dpll_pin_xa, ppin->id, DPLL_REGISTERED))
> +			continue;

What if unregister/unbind would happen right [here]?
[here]

>   		parent_priv = dpll_pin_on_dpll_priv(dpll_ref->dpll, ppin);
>   		ret = ops->state_on_pin_get(pin,
>   					    dpll_pin_on_pin_priv(ppin, pin),