On Mon, Jul 23, 2018 at 09:55:36PM +0000, Bart Van Assche wrote:
> On Mon, 2018-07-23 at 15:29 -0600, Jason Gunthorpe wrote:
> > On Wed, Jul 18, 2018 at 09:03:29AM -0700, Bart Van Assche wrote:
> > > This patch avoids that the following compiler warning is reported when
> > > building with gcc 8 and W=1:
> > >
> > > drivers/infiniband/hw/usnic/usnic_fwd.c:95:2: warning: 'strncpy' output may be truncated copying 16 bytes from a string of length 20 [-Wstringop-truncation]
> > > strncpy(ufdev->name, netdev_name(ufdev->netdev),
> > > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > sizeof(ufdev->name) - 1);
> > > ~~~~~~~~~~~~~~~~~~~~~~~~
> > >
> > > Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxx>
> > > Cc: Christian Benvenuti <benve@xxxxxxxxx>
> > > Cc: Dave Goodell <dgoodell@xxxxxxxxx>
> > > drivers/infiniband/hw/usnic/usnic_fwd.c | 3 +--
> > > 1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > I think this is a bug in netdev_name, it shouldn't return a constant
> > string longer than IFNAMSIZ.
>
> I think that netdev_name() was intended to be used for logging instead of to copying
> the result into an IFNAMSIZ array. See also commit 571ba4230381 ("netdevice.h: Add
> netdev_printk helpers like dev_printk"). How about something like the patch below?
>
> diff --git a/drivers/infiniband/hw/usnic/usnic_fwd.c b/drivers/infiniband/hw/usnic/usnic_fwd.c
> index 995a26b65156..e1a832775d2b 100644
> +++ b/drivers/infiniband/hw/usnic/usnic_fwd.c
> @@ -92,8 +92,7 @@ struct usnic_fwd_dev *usnic_fwd_dev_alloc(struct pci_dev *pdev)
> ufdev->pdev = pdev;
> ufdev->netdev = pci_get_drvdata(pdev);
> spin_lock_init(&ufdev->lock);
> - strncpy(ufdev->name, netdev_name(ufdev->netdev),
> - sizeof(ufdev->name) - 1);
> + strlcpy(ufdev->name, ufdev->netdev->name, sizeof(ufdev->name));
Okay, but now we don't need the strlcpy as it suppresses a useful
warning about truncation if the array lengths become mismatched
I'm leering about blanket replacing strncpy with strlcpy, almost
every case of truncation is actually a problem that should be solved
by preventing truncation or failing something..
Jason
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