linux-kernel - Re: [PATCH 1/3] staging: wilc1000: Remove reference preceded by free

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Date:	Mon, 26 Oct 2015 06:32:17 +0900
From:	Greg KH <gregkh@...uxfoundation.org>
To:	punit vara <punitvara@...il.com>
Cc:	johnny.kim@...el.com, rachel.kim@...el.com, chris.park@...el.com,
	tony.cho@...el.com, glen.lee@...el.com, leo.kim@...el.com,
	linux-wireless@...r.kernel.org, devel@...verdev.osuosl.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] staging: wilc1000: Remove reference preceded by free

On Mon, Oct 26, 2015 at 01:29:42AM +0530, punit vara wrote:
> On Mon, Oct 26, 2015 at 1:01 AM, punit vara <punitvara@...il.com> wrote:
> > On Mon, Oct 26, 2015 at 12:42 AM, Greg KH <gregkh@...uxfoundation.org> wrote:
> >> On Sun, Oct 25, 2015 at 04:01:23AM +0530, Punit Vara wrote:
> >>> This patch is to the wilc_wfi_cfgoperations.c file that fixes up
> >>> following error reported by coccicheck:
> >>>
> >>> ERROR: reference preceded by free on line 1219
> >>>
> >>> For (params->seq_len) <= 0 memory is already freed when
> >>> (params->seq_len) >0 then memory was alloted. So there is no need to use
> >>> kfree whenever params->seq_len <=0 remove it and place kfree inside
> >>> (params->seq_len) >0 condition.
> >>>
> >>> Signed-off-by: Punit Vara <punitvara@...il.com>
> >>> ---
> >>>  drivers/staging/wilc1000/wilc_wfi_cfgoperations.c | 7 +++----
> >>>  1 file changed, 3 insertions(+), 4 deletions(-)
> >>>
> >>> diff --git a/drivers/staging/wilc1000/wilc_wfi_cfgoperations.c b/drivers/staging/wilc1000/wilc_wfi_cfgoperations.c
> >>> index bcbf1bd..9b3cf04 100644
> >>> --- a/drivers/staging/wilc1000/wilc_wfi_cfgoperations.c
> >>> +++ b/drivers/staging/wilc1000/wilc_wfi_cfgoperations.c
> >>> @@ -1216,11 +1216,10 @@ static int add_key(struct wiphy *wiphy, struct net_device *netdev, u8 key_index,
> >>>
> >>>                               priv->wilc_ptk[key_index]->key = kmalloc(params->key_len, GFP_KERNEL);
> >>>
> >>> -                             kfree(priv->wilc_ptk[key_index]->seq);
> >>> -
> >>> -                             if ((params->seq_len) > 0)
> >>> +                             if ((params->seq_len) > 0) {
> >>> +                                     kfree(priv->wilc_ptk[key_index]->seq);
> >>>                                       priv->wilc_ptk[key_index]->seq = kmalloc(params->seq_len, GFP_KERNEL);
> >>> -
> >>> +                             }
> >>
> >> Are you sure about this?  It seems like you are changing the logic
> >> here...
> >>
> > Yes this time I am quite confident here . On This file line no 1177
> > already freed the allocation of memory ..On the following line if
> > (params->seq_len) > 0 then memory is allotted but if it is not then
> > memory allocation remains free only. So here kfree is not required
> > outside of the if condition. It should be inside the if condition
> > because for   (params->seq_len) > 0 memory is already allotted at line
> > followed by 1177. Kindly look at it once.
> >
> > Thanks :-)
> Again I went back thinking Greg who is stable kernel maintainer who
> doubts about logic .So I again go through these code , you are right .
> What you ignore this change and apply this patch ?
> diff --git a/drivers/staging/wilc1000/wilc_wfi_cfgoperations.c
> b/drivers/staging/wilc1000/wilc_wfi_cfgoperations.c
> index 9b3cf04..3ab7d3e 100644
> --- a/drivers/staging/wilc1000/wilc_wfi_cfgoperations.c
> +++ b/drivers/staging/wilc1000/wilc_wfi_cfgoperations.c
> @@ -1174,9 +1174,9 @@ static int add_key(struct wiphy *wiphy, struct
> net_device *netdev, u8 key_index,
>                                 memcpy(priv->wilc_gtk[key_index]->key,
> params->key, params->key_len);
> 
>                                 /* if there has been previous
> allocation for the same index through its seq, free that memory and
> allocate again*/
> -                               kfree(priv->wilc_gtk[key_index]->seq);
> 
>                                 if ((params->seq_len) > 0) {
> +                                       kfree(priv->wilc_gtk[key_index]->seq);
>                                         priv->wilc_gtk[key_index]->seq
> = kmalloc(params->seq_len, GFP_KERNEL);
> 
> memcpy(priv->wilc_gtk[key_index]->seq, params->seq, params->seq_len);
>                                 }
> 
> 
> ?? May send this patch ? I think it will not change the logic .
> Comment me if I am wrong

I don't really see the need for this change at all.  It's not fixing
anything, and the kfree call is "free" we don't need to worry about
that, so please, just leave it as-is for now, there is _so_ many other
real things to do to fix up this driver than to worry about
non-optimizing things like this.

thanks,

greg k-h
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