On Thu, Mar 28, 2019 at 09:51:56AM +0000, Li,Rongqing wrote:
> > -----邮件原件-----
> > 发件人: Michal Kubecek [mailto:mkube...@suse.cz]
> > 发送时间: 2019年3月28日 17:09
> > 收件人: Li,Rongqing <lirongq...@baidu.com>
> > 抄送: netdev@vger.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 <lirongq...@baidu.com>
> > > Reviewed-by: Wang Li <wangl...@baidu.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
stats is a local variable declared as
struct ethtool_stats stats;
where struct ethtool_stats which looks like
struct ethtool_stats {
__u32 cmd;
__u32 n_stats;
__u64 data[0];
};
so that storing anything to stats.data would result in stack corruption.
This is why ethtool_ops::get_ethtool_stats() has the third parameter
telling it where to put the statistics.
There isn't much point touching cmd and n_stats should be set to the
same value as we got from ethtool_ops::get_sset_counts earlier, i.e.
zero in our case.
Michal
