linux-kernel - Re: [PATCH net v4 1/4] dpll: fix pin dump crash for rebound module

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Message-ID: <Zafi9wid9HlbLM0z@nanopsycho>
Date: Wed, 17 Jan 2024 15:23:51 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>
Cc: netdev@...r.kernel.org, vadim.fedorenko@...ux.dev, davem@...emloft.net,
	milena.olech@...el.com, linux-kernel@...r.kernel.org,
	pabeni@...hat.com, kuba@...nel.org, mschmidt@...hat.com,
	Jan Glaza <jan.glaza@...el.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>
Subject: Re: [PATCH net v4 1/4] dpll: fix pin dump crash for rebound module

Wed, Jan 17, 2024 at 10:14:13AM CET, arkadiusz.kubalewski@...el.com wrote:
>When a kernel module is unbound but the pin resources were not entirely
>freed (other kernel module instance of the same PCI device have had kept
>the reference to that pin), and kernel module is again bound, the pin
>properties would not be updated (the properties are only assigned when
>memory for the pin is allocated), prop pointer still points to the
>kernel module memory of the kernel module which was deallocated on the
>unbind.
>
>If the pin dump is invoked in this state, the result is a kernel crash.
>Prevent the crash by storing persistent pin properties in dpll subsystem,
>copy the content from the kernel module when pin is allocated, instead of
>using memory of the kernel module.
>
>Fixes: 9431063ad323 ("dpll: core: Add DPLL framework base functions")
>Fixes: 9d71b54b65b1 ("dpll: netlink: Add DPLL framework base functions")
>Reviewed-by: Jan Glaza <jan.glaza@...el.com>
>Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@...el.com>
>Signed-off-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>

[...]


>@@ -443,7 +490,9 @@ dpll_pin_alloc(u64 clock_id, u32 pin_idx, struct module *module,
> 		ret = -EINVAL;
> 		goto err;
> 	}
>-	pin->prop = prop;
>+	ret = dpll_pin_prop_dup(prop, &pin->prop);
>+	if (ret)
>+		goto pin_free;

This does not compile, does it? Please fix the error path first (patch
4 should be patch 1) and then use properly named label right away there.

pw-bot: cr


> 	refcount_set(&pin->refcount, 1);
> 	xa_init_flags(&pin->dpll_refs, XA_FLAGS_ALLOC);
> 	xa_init_flags(&pin->parent_refs, XA_FLAGS_ALLOC);

[...]