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

From: Pavel Machek
Date: Thu Nov 21 2019 - 05:35:08 EST


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

Attachment: signature.asc
Description: Digital signature