linux-kernel - Re: [PATCH next] wifi: iwlwifi: Fix uninitialized variable with _

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Message-ID: <a21610ae-e155-44bc-bcc5-b9b8b1c8cbd1@oss.qualcomm.com>
Date: Wed, 12 Mar 2025 08:15:18 -0700
From: Jeff Johnson <jeff.johnson@....qualcomm.com>
To: Dan Carpenter <dan.carpenter@...aro.org>,
        Miri Korenblit <miriam.rachel.korenblit@...el.com>
Cc: Johannes Berg <johannes.berg@...el.com>,
        Anjaneyulu <pagadala.yesu.anjaneyulu@...el.com>,
        Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        Avraham Stern <avraham.stern@...el.com>,
        Yedidya Benshimol <yedidya.ben.shimol@...el.com>,
        Daniel Gabay <daniel.gabay@...el.com>, linux-wireless@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH next] wifi: iwlwifi: Fix uninitialized variable with
 __free()

On 3/12/2025 1:31 AM, Dan Carpenter wrote:
> Pointers declared with the __free(kfree) attribute need to be initialized
> because they will be passed to kfree() on every return path.  There are
> two return statement before the "cmd" pointer is initialized so this
> leads to an uninitialized variable bug.
> 
> Fixes: d1e879ec600f ("wifi: iwlwifi: add iwlmld sub-driver")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---
>  drivers/net/wireless/intel/iwlwifi/mld/debugfs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/intel/iwlwifi/mld/debugfs.c b/drivers/net/wireless/intel/iwlwifi/mld/debugfs.c
> index c759c5c68dc0..1d4b2ad5d388 100644
> --- a/drivers/net/wireless/intel/iwlwifi/mld/debugfs.c
> +++ b/drivers/net/wireless/intel/iwlwifi/mld/debugfs.c
> @@ -556,8 +556,8 @@ iwl_dbgfs_vif_twt_setup_write(struct iwl_mld *mld, char *buf, size_t count,
>  	};
>  	struct ieee80211_vif *vif = data;
>  	struct iwl_mld_vif *mld_vif = iwl_mld_vif_from_mac80211(vif);
> +	struct iwl_dhc_cmd *cmd __free(kfree) = NULL;

hmm, I thought the recommended convention was to define __free() pointers at
the point of allocation. cleanup.h explicitly says:

 * Given that the "__free(...) = NULL" pattern for variables defined at
 * the top of the function poses this potential interdependency problem
 * the recommendation is to always define and assign variables in one
 * statement and not group variable definitions at the top of the
 * function when __free() is used.

>  	struct iwl_dhc_twt_operation *dhc_twt_cmd;
> -	struct iwl_dhc_cmd *cmd __free(kfree);
>  	u64 target_wake_time;
>  	u32 twt_operation, interval_exp, interval_mantissa, min_wake_duration;
>  	u8 trigger, flow_type, flow_id, protection, tenth_param;