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

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Message-ID: <341d748f-55ae-451b-983a-ca9684d265b7@stanley.mountain>
Date: Wed, 12 Mar 2025 18:24:58 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Jeff Johnson <jeff.johnson@....qualcomm.com>
Cc: Miri Korenblit <miriam.rachel.korenblit@...el.com>,
	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 Wed, Mar 12, 2025 at 08:15:18AM -0700, Jeff Johnson wrote:
> 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.
> 

People do it either way.  I'm agnostic so long as it doesn't have bugs.

regards,
dan carpenter