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Date: Tue, 23 Aug 2016 08:05:16 -0700 From: Joe Perches <joe@...ches.com> To: Eric Dumazet <eric.dumazet@...il.com>, Luis Henriques <luis.henriques@...onical.com> Cc: Avijit Kanti Das <avijitnsec@...eaurora.org>, "David S . Miller" <davem@...emloft.net>, Ben Hutchings <ben@...adent.org.uk>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: net: Zeroing the structure ethtool_wolinfo in ethtool_get_wol() 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 <avijitnsec@...eaurora.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?
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