> -----邮件原件----- > 发件人: Michal Kubecek [mailto:mkube...@suse.cz] > 发送时间: 2019年3月28日 18:26 > 收件人: Li,Rongqing <lirongq...@baidu.com> > 抄送: netdev@vger.kernel.org > 主题: Re: 答复: [PATCH] net: ethtool: not call vzalloc for zero sized memory > request > > 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. >
Ok, I will send v2 which does not call ops->get_ethtool_stats, if n_stats is 0 Thanks -RongQing > Michal
