linux-kernel - Re: [PATCH] staging: gdm72xx: add userspace data struct

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Date:	Thu, 10 Dec 2015 14:34:21 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Wim de With <nauxuron@...dewith.com>
Cc:	devel@...verdev.osuosl.org, gregkh@...uxfoundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: gdm72xx: add userspace data struct

On Thu, Dec 10, 2015 at 10:42:14AM +0100, Wim de With wrote:
> On 10-12-2015 10:37, Dan Carpenter wrote:
> > On Thu, Dec 10, 2015 at 10:11:12AM +0100, Wim de With wrote:
> >> @@ -482,8 +483,16 @@ static int gdm_wimax_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
> >>  				/* NOTE: gdm_update_fsm should be called
> >>  				 * before gdm_wimax_ioctl_set_data is called.
> >>  				 */
> >> -				gdm_update_fsm(dev,
> >> -					       req->data.buf);
> >> +				fsm_buf = kmalloc(sizeof(fsm_s), GFP_KERNEL);
> >> +				if (!fsm_buf)
> >> +					return -ENOMEM;
> >> +				if (copy_from_user(fsm_buf, req->data.buf,
> >> +						   sizeof(fsm_s))) {
> >> +					kfree(fsm_buf);
> >> +					return -EFAULT;
> >> +				}
> >> +				gdm_update_fsm(dev, fsm_buf);
> >> +				kfree(fsm_buf);
> > 
> > 
> > No.  This change is a bug.
> > 
> > regards,
> > dan carpenter
> > 
> 
> But what if I just keep it as:
> 
> 	gdm_update_fsm(dev, req->data.buf)
> 
> Then it would just trust a __user pointer right?

I appologize, I didn't read the patch carefully.  This is a bugfix.  Can
you resend the patch with a better patch description where you replace
the last paragraph and say:

Once I updated the Sparse annotations, I noticed a bug in
gdm_wimax_ioctl() where we pass a user space pointer to gdm_update_fsm()
which dereferences it.  I fixed this.

regards,
dan carpenter
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