linux-kernel - Re: [PATCH net] ice: Fix freeing uninitialized pointers

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Message-ID: <d2b1f3bd-42f1-483b-916e-3735b39a30e1@web.de>
Date: Thu, 21 Mar 2024 18:59:00 +0100
From: Markus Elfring <Markus.Elfring@....de>
To: Dan Carpenter <dan.carpenter@...aro.org>,
 kernel-janitors@...r.kernel.org, netdev@...r.kernel.org,
 intel-wired-lan@...ts.osuosl.org,
 Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
 Przemek Kitszel <przemyslaw.kitszel@...el.com>,
 Tony Nguyen <anthony.l.nguyen@...el.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Alexander Lobakin <aleksander.lobakin@...el.com>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 David Laight <David.Laight@...lab.com>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>,
 Jesse Brandeburg <jesse.brandeburg@...el.com>, Jiri Pirko
 <jiri@...nulli.us>, Jonathan Cameron <jic23@...nel.org>,
 Julia Lawall <julia.lawall@...ia.fr>, Kees Cook <keescook@...omium.org>,
 Lukasz Czapnik <lukasz.czapnik@...el.com>, Paolo Abeni <pabeni@...hat.com>,
 Pucha Himasekhar Reddy <himasekharx.reddy.pucha@...el.com>
Subject: Re: [PATCH net] ice: Fix freeing uninitialized pointers

> Automatically cleaned up pointers need to be initialized before exiting
> their scope.  In this case, they need to be initialized to NULL before
> any return statement.

How will development interests evolve further for such design aspects?

…
> +++ b/drivers/net/ethernet/intel/ice/ice_ethtool.c
> @@ -941,11 +941,11 @@ static u64 ice_loopback_test(struct net_device *netdev)
>  	struct ice_netdev_priv *np = netdev_priv(netdev);
>  	struct ice_vsi *orig_vsi = np->vsi, *test_vsi;
>  	struct ice_pf *pf = orig_vsi->back;
> +	u8 *tx_frame __free(kfree) = NULL;
>  	u8 broadcast[ETH_ALEN], ret = 0;
>  	int num_frames, valid_frames;
>  	struct ice_tx_ring *tx_ring;
>  	struct ice_rx_ring *rx_ring;
> -	u8 *tx_frame __free(kfree);
>  	int i;
>
>  	netdev_info(netdev, "loopback test\n");

How do you think about to reduce the scope for the affected local variable instead
with the help of a small script (like the following) for the semantic patch language?

@movement@
attribute name __free;
@@
-u8 *tx_frame __free(kfree);
 int i;
 ... when any
 if (ice_fltr_add_mac(test_vsi, ...))
 { ... }
+
+{
+u8 *tx_frame __free(kfree) = NULL;
 if (ice_lbtest_create_frame(pf, &tx_frame, ...))
 { ... }
 ... when any
+}
+
 valid_frames = ice_lbtest_receive_frames(...);

Regards,
Markus