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

From: Jiri Pirko <[email-masked]>
Date: Wed, 8 Nov 2023 16:08:42 +0100

Wed, Nov 08, 2023 at 11:32:24AM CET, [email-masked] 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 <[email-masked]>
>---
> 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

Read this sentence like 10 times, still don't get what you mean.
Shouldn't comments be easy to understand?

>+		 */
>+		if (!xa_get_mark(&dpll_pin_xa, ppin->id, DPLL_REGISTERED))
>+			continue;
> 		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),
>-- 
>2.38.1
>