linux-kernel - Re: [PATCH 3/4] net: usb: rtl8150: use usb_control_msg_recv() and usb_control_msg

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Date:   Wed, 23 Sep 2020 17:48:32 +0300
From:   Petko Manolov <petkan@...leusys.com>
To:     Oliver Neukum <oneukum@...e.com>
Cc:     Himadri Pandya <himadrispandya@...il.com>, davem@...emloft.net,
        kuba@...nel.org, pankaj.laxminarayan.bharadiya@...el.com,
        keescook@...omium.org, yuehaibing@...wei.com, ogiannou@...il.com,
        linux-usb@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        gregkh@...uxfoundation.org
Subject: Re: [PATCH 3/4] net: usb: rtl8150: use usb_control_msg_recv() and
 usb_control_msg_send()

On 20-09-23 12:22:37, Oliver Neukum wrote:
> Am Mittwoch, den 23.09.2020, 14:35 +0530 schrieb Himadri Pandya:
> 
> Hi,
> 
> > Many usage of usb_control_msg() do not have proper error check on return
> > value leaving scope for bugs on short reads. New usb_control_msg_recv()
> > and usb_control_msg_send() nicely wraps usb_control_msg() with proper
> > error check. Hence use the wrappers instead of calling usb_control_msg()
> > directly.
> > 
> > Signed-off-by: Himadri Pandya <himadrispandya@...il.com>
> Nacked-by: Oliver Neukum <oneukum@...e.com>
> 
> > ---
> >  drivers/net/usb/rtl8150.c | 32 ++++++--------------------------
> >  1 file changed, 6 insertions(+), 26 deletions(-)
> > 
> > diff --git a/drivers/net/usb/rtl8150.c b/drivers/net/usb/rtl8150.c
> > index 733f120c852b..e3002b675921 100644
> > --- a/drivers/net/usb/rtl8150.c
> > +++ b/drivers/net/usb/rtl8150.c
> > @@ -152,36 +152,16 @@ static const char driver_name [] = "rtl8150";
> >  */
> >  static int get_registers(rtl8150_t * dev, u16 indx, u16 size, void *data)
> >  {
> > -	void *buf;
> > -	int ret;
> > -
> > -	buf = kmalloc(size, GFP_NOIO);
> 
> GFP_NOIO is used here for a reason. You need to use this helper
> while in contexts of error recovery and runtime PM.
> 
> > -	if (!buf)
> > -		return -ENOMEM;
> > -
> > -	ret = usb_control_msg(dev->udev, usb_rcvctrlpipe(dev->udev, 0),
> > -			      RTL8150_REQ_GET_REGS, RTL8150_REQT_READ,
> > -			      indx, 0, buf, size, 500);
> > -	if (ret > 0 && ret <= size)
> > -		memcpy(data, buf, ret);
> > -	kfree(buf);
> > -	return ret;
> > +	return usb_control_msg_recv(dev->udev, 0, RTL8150_REQ_GET_REGS,
> > +				    RTL8150_REQT_READ, indx, 0, data,
> > +				    size, 500);
> 
> This internally uses kmemdup() with GFP_KERNEL.
> You cannot make this change. The API does not support it.
> I am afraid we will have to change the API first, before more
> such changes are done.

One possible fix is to add yet another argument to usb_control_msg_recv(), which 
would be the GFP_XYZ flag to pass on to kmemdup().  Up to Greg, of course.


cheers,
Petko