linux-kernel - Re: [PATCH -next] drivers: w1: use kfree

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Message-ID: <YoOnrsEAFOclLbG2@kroah.com>
Date:   Tue, 17 May 2022 15:48:30 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Yang Yingliang <yangyingliang@...wei.com>
Cc:     linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
        zbr@...emap.net, jdelvare@...e.com, linux@...ck-us.net
Subject: Re: [PATCH -next] drivers: w1: use kfree_sensitive()

On Tue, May 17, 2022 at 09:03:43PM +0800, Yang Yingliang wrote:
> 
> On 2022/5/17 18:18, Greg KH wrote:
> > On Wed, May 11, 2022 at 03:25:52PM +0800, Yang Yingliang wrote:
> > > Hi,
> > > 
> > > On 2022/5/11 14:45, Greg KH wrote:
> > > > On Wed, May 11, 2022 at 02:49:54PM +0800, Yang Yingliang wrote:
> > > > > Use kfree_sensitive() instead of open-coding it.
> > > > > 
> > > > > Signed-off-by: Yang Yingliang <yangyingliang@...wei.com>
> > > > > ---
> > > > >    drivers/w1/w1.c | 3 +--
> > > > >    1 file changed, 1 insertion(+), 2 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c
> > > > > index f2ae2e563dc5..a0a6c3c739d9 100644
> > > > > --- a/drivers/w1/w1.c
> > > > > +++ b/drivers/w1/w1.c
> > > > > @@ -73,8 +73,7 @@ static void w1_master_release(struct device *dev)
> > > > >    	struct w1_master *md = dev_to_w1_master(dev);
> > > > >    	dev_dbg(dev, "%s: Releasing %s.\n", __func__, md->name);
> > > > > -	memset(md, 0, sizeof(struct w1_master) + sizeof(struct w1_bus_master));
> > > > > -	kfree(md);
> > > > > +	kfree_sensitive(md);
> > > > Does this actually change anything?  Why is the memset being called here
> > > > at all?
> > > It's no functional change and I got this by
> > > scripts/coccinelle/api/kfree_sensitive.cocci.
> > > I'm not sure why using memset() here.
> > I think the memset() can just be dropped.  Can you make that change and
> > test it to verify it still works properly with that change?
> I can make change and send a patch for this, but I don't have device to test
> it.

For something like this, it would be great to test.

thanks,

greg k-h