linux-kernel - Re: [PATCH] staging: media: atomisp: Use kvfree

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Date:   Wed, 9 Sep 2020 23:06:51 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Alex Dewar <alex.dewar90@...il.com>
Cc:     devel@...verdev.osuosl.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org
Subject: Re: [PATCH] staging: media: atomisp: Use kvfree_sensitive in a few
 places

On Wed, Sep 09, 2020 at 08:53:50PM +0100, Alex Dewar wrote:
> In the file pci/sh_css_params.c, there are a number of places where
> memset+kvfree is used, where kvfree_sensitive could be used instead. Fix
> these occurrences.

This doesn't say *why* the commit is doing it.  There are two reasons:
The worry with these is that the compiler could optimize away the memset
because it sees the kfree().  Second using kvfree_sensitive() is more
clear and readable.

> 
> Issue identified with Coccinelle.
> 
> Signed-off-by: Alex Dewar <alex.dewar90@...il.com>
> ---
>  .../staging/media/atomisp/pci/sh_css_params.c | 19 +++++++------------
>  1 file changed, 7 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/staging/media/atomisp/pci/sh_css_params.c b/drivers/staging/media/atomisp/pci/sh_css_params.c
> index 2c67c23b3700..d1b5d6608d52 100644
> --- a/drivers/staging/media/atomisp/pci/sh_css_params.c
> +++ b/drivers/staging/media/atomisp/pci/sh_css_params.c
> @@ -4378,8 +4378,7 @@ ia_css_3a_statistics_free(struct ia_css_3a_statistics *me)
>  	if (me) {
>  		kvfree(me->rgby_data);
>  		kvfree(me->data);
> -		memset(me, 0, sizeof(struct ia_css_3a_statistics));
> -		kvfree(me);
> +		kvfree_sensitive(me, sizeof(struct ia_css_3a_statistics));

I don't think ia_css_3a_statistics are sensitive at all.  What we're
trying to protect are things like passwords.  Just delete the memset.

Looking below, I don't think any of these are sensitive so just delete
all the memsets.

regards,
dan carpenter