linux-kernel - Re: [PATCH] fix error handling in drivers/staging/rtl8192u/ieee80211/ieee80211

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Date:   Thu, 27 Sep 2018 17:24:03 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     valdis.kletnieks@...edu
Cc:     gregkh@...uxfoundation.org, John Whitmore <arigead@...il.com>,
        Kees Cook <keescook@...omium.org>, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, kernelnewbies@...nelnewbies.org
Subject: Re: [PATCH] fix error handling in
 drivers/staging/rtl8192u/ieee80211/ieee80211_module.c

On Wed, Sep 26, 2018 at 01:52:17PM -0400, valdis.kletnieks@...edu wrote:
> John notes that if the kzalloc of ieee->pHTInfo fails, we fail to call
> ieee80211_networks_free().  In addition, that function has an un-needed check
> before kfree().
> 
> Reported-by: John Whitmore <arigead@...il.com>
> Signed-off-by: Valdis Kletnieks <valdis.kletnieks@...edu>
> ---
> diff --git a/drivers/staging/rtl8192u/ieee80211/ieee80211_module.c b/drivers/staging/rtl8192u/ieee80211/ieee80211_module.c
> index 90a097f2cd4e..97ff0371b5bb 100644
> --- a/drivers/staging/rtl8192u/ieee80211/ieee80211_module.c
> +++ b/drivers/staging/rtl8192u/ieee80211/ieee80211_module.c
> @@ -78,8 +78,6 @@ static inline int ieee80211_networks_allocate(struct ieee80211_device *ieee)
>  
>  static inline void ieee80211_networks_free(struct ieee80211_device *ieee)
>  {
> -	if (!ieee->networks)
> -		return;
>  	kfree(ieee->networks);
>  	ieee->networks = NULL;
>  }
> @@ -180,6 +178,7 @@ struct net_device *alloc_ieee80211(int sizeof_priv)
>  	return dev;
>  
>   failed:
> +	ieee80211_networks_free(ieee);
>  	if (dev)
>  		free_netdev(dev);

When there is a "goto failed;" then it's called "one err style" error
handling and we're just asking for bugs...  In this case the bug is that
we're not allowd to call ieee80211_networks_free() with a NULL
"ieee" parameter.  The right thing to do is to only call
ieee80211_networks_free() if we know that ieee80211_networks_allocate()
succeeded.

regards,
dan carpenter