On Tue, 2016-08-23 at 07:21 -0700, Eric Dumazet wrote:
> On Tue, 2016-08-23 at 14:41 +0100, Luis Henriques wrote:
> > From: Avijit Kanti Das <avijitn...@codeaurora.org>
> >
> > memset() the structure ethtool_wolinfo that has padded bytes
> > but the padded bytes have not been zeroed out.
[]
> > diff --git a/net/core/ethtool.c b/net/core/ethtool.c
[]
> > @@ -1435,11 +1435,13 @@ static int ethtool_reset(struct net_device *dev,
> > char __user *useraddr)
> >
> > static int ethtool_get_wol(struct net_device *dev, char __user *useraddr)
> > {
> > - struct ethtool_wolinfo wol = { .cmd = ETHTOOL_GWOL };
> > + struct ethtool_wolinfo wol;
> >
> > if (!dev->ethtool_ops->get_wol)
> > return -EOPNOTSUPP;
> >
> > + memset(&wol, 0, sizeof(struct ethtool_wolinfo));
> > + wol.cmd = ETHTOOL_GWOL;
> > dev->ethtool_ops->get_wol(dev, &wol);
> >
> > if (copy_to_user(useraddr, &wol, sizeof(wol)))
> This would suggest a compiler bug to me.
A compiler does not have a standards based requirement to
initialize arbitrary padding bytes.
I believe gcc always does zero all padding anyway.
> I checked that my compiler does properly put zeros there, even in the
> padding area.
>
> If we can not rely on such constructs, we have hundreds of similar
> patches to submit.
True.
>From a practical point of view, does any compiler used for
kernel compilation (gcc/icc/llvm/any others?) not always
perform zero padding of alignment bytes?
