RE: [PATCH 4.19 079/422] i40e: use correct length for strncpy

[Williams, Mitch A]

> -----Original Message-----
> From: Pavel Machek <pavel@xxxxxxx>
> Sent: Thursday, November 21, 2019 2:35 AM
> To: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx; Williams, Mitch A
> <mitch.a.williams@xxxxxxxxx>; Bowers, AndrewX <andrewx.bowers@xxxxxxxxx>;
> Kirsher, Jeffrey T <jeffrey.t.kirsher@xxxxxxxxx>; Sasha Levin
> <sashal@xxxxxxxxxx>
> Subject: Re: [PATCH 4.19 079/422] i40e: use correct length for strncpy
> 
> Hi!
> 
> > From: Mitch Williams <mitch.a.williams@xxxxxxxxx>
> >
> > [ Upstream commit 7eb74ff891b4e94b8bac48f648a21e4b94ddee64 ]
> >
> > Caught by GCC 8. When we provide a length for strncpy, we should not
> > include the terminating null. So we must tell it one less than the size
> > of the destination buffer.
> 
> > +++ b/drivers/net/ethernet/intel/i40e/i40e_ptp.c
> > @@ -694,7 +694,8 @@ static long i40e_ptp_create_clock(struct i40e_pf *pf)
> >  	if (!IS_ERR_OR_NULL(pf->ptp_clock))
> >  		return 0;
> >
> > -	strncpy(pf->ptp_caps.name, i40e_driver_name, sizeof(pf->ptp_caps.name));
> > +	strncpy(pf->ptp_caps.name, i40e_driver_name,
> > +		sizeof(pf->ptp_caps.name) - 1);
> >  	pf->ptp_caps.owner = THIS_MODULE;
> >  	pf->ptp_caps.max_adj = 999999999;
> >  	pf->ptp_caps.n_ext_ts = 0;
> 
> So... pf is allocated with kzalloc, which will provide the null
> termination... so the code is okay.
> 
> On the other hand, the = 0 below is unneeded by the same logic, so
> this is a bit confusing.
> 
> Best regards,
> 								Pavel

Thanks for catching this, Pavel. Aleksandr Loktionov owns this driver now. He can get this taken care of.
-Mitch


> --
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures)
> http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html