[U-Boot] [PATCH] drivers: usb: fsl: Fix NULL terminating issue for usb controller name string

[Rajesh Bhagat]

> -----Original Message-----
> From: Marek Vasut [mailto:marex at denx.de]
> Sent: Wednesday, June 01, 2016 6:51 PM
> To: Rajesh Bhagat <rajesh.bhagat at nxp.com>; u-boot at lists.denx.de
> Cc: york sun <york.sun at nxp.com>; Sriram Dash <sriram.dash at nxp.com>
> Subject: Re: [PATCH] drivers: usb: fsl: Fix NULL terminating issue for usb controller
> name string
> 
> On 06/01/2016 01:17 PM, Rajesh Bhagat wrote:
> > Fixes NULL terminating issue for usb controller name string and
> > performs code cleanup for intializing variables current_usb_controller
> > and usb_phy.
> >
> > Signed-off-by: Rajesh Bhagat <rajesh.bhagat at nxp.com>
> > ---
> >  drivers/usb/host/ehci-fsl.c |   10 ++++------
> >  1 files changed, 4 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/usb/host/ehci-fsl.c b/drivers/usb/host/ehci-fsl.c
> > index a43d37d..a806993 100644
> > --- a/drivers/usb/host/ehci-fsl.c
> > +++ b/drivers/usb/host/ehci-fsl.c
> > @@ -49,11 +49,9 @@ int ehci_hcd_init(int index, enum usb_init_type init,
> >  	struct usb_ehci *ehci = NULL;
> >  	const char *phy_type = NULL;
> >  	size_t len;
> > -	char current_usb_controller[5];
> > +	char current_usb_controller[5] = {0};
> >  #ifdef CONFIG_SYS_FSL_USB_INTERNAL_UTMI_PHY
> > -	char usb_phy[5];
> > -
> > -	usb_phy[0] = '\0';
> > +	char usb_phy[5] = {0};
> >  #endif
> >  	if (has_erratum_a007075()) {
> >  		/*
> > @@ -64,8 +62,8 @@ int ehci_hcd_init(int index, enum usb_init_type init,
> >  		 */
> >  		mdelay(5);
> >  	}
> > -	memset(current_usb_controller, '\0', 5);
> > -	snprintf(current_usb_controller, 4, "usb%d", index+1);
> > +	snprintf(current_usb_controller, sizeof(current_usb_controller),
> > +		 "usb%d", index+1);
> 
> What is the actual problem here ? snprintf() will add the \0 at the end of the string, so
> I don't see any "null terminating issue" in the code.
> I can understand using the sizeof() in the snprintf(), which is valid, but that's all.
> 

Hello Marek, 

It is surprising for me too, but same can be verified even on x86 machine using below test 
program, Can it be compiler optimization of memset?

Output #1 : current_usb_controller usb
Output #2 : current_usb_controller usb1 (Expected Output)

int main()
{
        int index = 0;
#if 1  
        char current_usb_controller[5];
        memset(current_usb_controller, '\0', 5);                        
        snprintf(current_usb_controller, 4, "usb%d", index+1);
#else
        char current_usb_controller[5] = {0};
        snprintf(current_usb_controller, sizeof(current_usb_controller), "usb%d", index+1);
#endif

        printf("current_usb_controller %s\n", current_usb_controller);
        return 0;
}

Best Regards,
Rajesh Bhagat 

> >  	switch (index) {
> >  	case 0:
> >
> 
> 
> --
> Best regards,
> Marek Vasut