linux-kernel - Re: [PATCH] usb: Use memdup

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Date:	Tue, 8 Dec 2015 14:51:57 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	"Pathak, Rahul (R.)" <rpathak@...teon.com>
Cc:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"stern@...land.harvard.edu" <stern@...land.harvard.edu>,
	"kborer@...il.com" <kborer@...il.com>,
	"chasemetzger15@...il.com" <chasemetzger15@...il.com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: Use memdup_user to reuse the code

On Tue, Dec 08, 2015 at 11:38:59AM +0000, Pathak, Rahul (R.) wrote:
> diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
> index 38ae877c..05266f0 100644
> --- a/drivers/usb/core/devio.c
> +++ b/drivers/usb/core/devio.c
> @@ -1395,11 +1395,9 @@ static int proc_do_submiturb(struct usb_dev_state *ps, struct usbdevfs_urb *uurb
>  		number_of_packets = uurb->number_of_packets;
>  		isofrmlen = sizeof(struct usbdevfs_iso_packet_desc) *
>  				   number_of_packets;
> -		isopkt = kmalloc(isofrmlen, GFP_KERNEL);
> -		if (!isopkt)
> -			return -ENOMEM;
> -		if (copy_from_user(isopkt, iso_frame_desc, isofrmlen)) {
> -			ret = -EFAULT;
> +		isopkt = memdup_user(iso_frame_desc, isofrmlen);
> +		if (IS_ERR(isopkt)) {
> +			ret = PTR_ERR(isopkt);
>  			goto error;

This introduces a one err bug.
https://plus.google.com/106378716002406849458/posts/dnanfhQ4mHQ
We can't call kfree(isopkt) when it is an ERR_PTR.

Set it to NULL:

		isopkt = memdup_user(iso_frame_desc, isofrmlen);
		if (IS_ERR(isopkt)) {
			ret = PTR_ERR(isopkt);
			isopkt = NULL;
			goto error;
		}

regards,
dan carpenter

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