linux-kernel - Re: [RFC 7/7] USB: usbatm: avoid fragile and inefficient snprintf use

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Date:	Thu, 10 Mar 2016 15:56:42 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Joe Perches <joe@...ches.com>
Cc:	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Kees Cook <keescook@...omium.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Duncan Sands <duncan.sands@...e.fr>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC 7/7] USB: usbatm: avoid fragile and inefficient snprintf use

On Tue, Mar 08, 2016 at 01:01:09PM -0800, Joe Perches wrote:
> On Tue, 2016-03-08 at 21:40 +0100, Rasmus Villemoes wrote:
> > Passing overlapping source and destination is fragile, and in this
> > case we can even simplify the code and avoid the huge stack buffer by
> > using the %p extension for printing a small hex dump.
> []
> > diff --git a/drivers/usb/atm/usbatm.c b/drivers/usb/atm/usbatm.c
> []
> > @@ -1331,15 +1331,12 @@ MODULE_VERSION(DRIVER_VERSION);
> >  static int usbatm_print_packet(struct usbatm_data *instance,
> >  			       const unsigned char *data, int len)
> >  {
> > -	unsigned char buffer[256];
> > -	int i = 0, j = 0;
> > +	int i, j;
> >  
> >  	for (i = 0; i < len;) {
> > -		buffer[0] = '\0';
> > -		sprintf(buffer, "%.3d :", i);
> > -		for (j = 0; (j < 16) && (i < len); j++, i++)
> > -			sprintf(buffer, "%s %2.2x", buffer, data[i]);
> > -		dev_dbg(&instance->usb_intf->dev, "%s", buffer);
> > +		j = min(16, len-i);
> > +		dev_dbg(&instance->usb_intf->dev, "%.3d : %*ph", i, j, data + i);
> > +		i += j;
> >  	}
> >  	return i;
> >  }
> 
> Maybe use print_dump_hex_debug()

Yes, please use that instead.