netdev - 答复: [PATCH] net: ethtool: not call vzalloc for zero sized memory request

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Date:   Thu, 28 Mar 2019 09:51:56 +0000
From:   "Li,Rongqing" <lirongqing@...du.com>
To:     Michal Kubecek <mkubecek@...e.cz>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: 答复: [PATCH] net: ethtool: not call vzalloc for zero sized memory request



> -----邮件原件-----
> 发件人: Michal Kubecek [mailto:mkubecek@...e.cz]
> 发送时间: 2019年3月28日 17:09
> 收件人: Li,Rongqing <lirongqing@...du.com>
> 抄送: netdev@...r.kernel.org
> 主题: Re: [PATCH] net: ethtool: not call vzalloc for zero sized memory request
> 
> On Thu, Mar 28, 2019 at 02:01:09PM +0800, Li RongQing wrote:
> > NULL or ZERO_SIZE_PTR will be returned for zero sized memory request,
> > and derefencing them will lead to a segfault
> >
> > so it is unnecessory to call vzalloc for zero sized memory request and
> > not call __ethtool_get_strings which always uses the allocated memory
> >
> > this also fixes a possible memory leak if phy_ethtool_get_stats
> > returns error, memory should be freed before exit
> >
> > Signed-off-by: Li RongQing <lirongqing@...du.com>
> > Reviewed-by: Wang Li <wangli39@...du.com>
> > ---
> >  net/core/ethtool.c | 37 ++++++++++++++++++++++++++-----------
> >  1 file changed, 26 insertions(+), 11 deletions(-)
> >
> > diff --git a/net/core/ethtool.c b/net/core/ethtool.c index
> > b1eb32419732..3e971a36e37c 100644
> > --- a/net/core/ethtool.c
> > +++ b/net/core/ethtool.c
> ...
> > @@ -1897,9 +1902,14 @@ static int ethtool_get_stats(struct net_device
> *dev, void __user *useraddr)
> >  		return -EFAULT;
> >
> >  	stats.n_stats = n_stats;
> > -	data = vzalloc(array_size(n_stats, sizeof(u64)));
> > -	if (n_stats && !data)
> > -		return -ENOMEM;
> > +
> > +	if (n_stats) {
> > +		data = vzalloc(array_size(n_stats, sizeof(u64)));
> > +		if (!data)
> > +			return -ENOMEM;
> > +	} else {
> > +		data = NULL;
> > +	}
> >
> >  	ops->get_ethtool_stats(dev, &stats, data);
> >
> 
> You avoid the vzalloc() call here but you still pass null data pointer to device's
> get_ethtool_stats() handler which seems to contradict what the commit
> message says. Is it really what you want? (The same applies to
> ethtool_get_phy_stats() below.)
> 


I keep it deliberately

ops->get_ethtool_stats(dev, &stats, data) have three parameter, 
if n_stats is 0 [we assume the returning 0 of ops->get_sset_count is correct, or 
get_sset_count should be fixed], data is NULL,  get_ethtool_stats () maybe still 
store the data into its seconds parameter, stats, even if I did not find which drivers
is like that


but __ethtool_get_strings is different, only one place to store data, so
if count is 0, __ethtool_get_strings does not need to be called

-RongQing



> Michal
> 
> > @@ -1941,14 +1951,19 @@ static int ethtool_get_phy_stats(struct
> net_device *dev, void __user *useraddr)
> >  		return -EFAULT;
> >
> >  	stats.n_stats = n_stats;
> > -	data = vzalloc(array_size(n_stats, sizeof(u64)));
> > -	if (n_stats && !data)
> > -		return -ENOMEM;
> > +
> > +	if (n_stats) {
> > +		data = vzalloc(array_size(n_stats, sizeof(u64)));
> > +		if (!data)
> > +			return -ENOMEM;
> > +	} else {
> > +		data = NULL;
> > +	}
> >
> >  	if (dev->phydev && !ops->get_ethtool_phy_stats) {
> >  		ret = phy_ethtool_get_stats(dev->phydev, &stats, data);
> >  		if (ret < 0)
> > -			return ret;
> > +			goto out;
> >  	} else {
> >  		ops->get_ethtool_phy_stats(dev, &stats, data);
> >  	}
> > --
> > 2.16.2
> >