netdev - Re: Re: [PATCH] ethernet:enic: Fix a use after free bug in enic_hard_start

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Date:   Sun, 2 May 2021 20:00:20 +0800 (GMT+08:00)
From:   lyl2019@...l.ustc.edu.cn
To:     "Govindarajulu Varadarajan (gvaradar)" <gvaradar@...co.com>
Cc:     "Christian Benvenuti (benve)" <benve@...co.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Re: [PATCH] ethernet:enic: Fix a use after free bug in
 enic_hard_start_xmit




> -----原始邮件-----
> 发件人: "Govindarajulu Varadarajan (gvaradar)" <gvaradar@...co.com>
> 发送时间: 2021-05-02 09:12:49 (星期日)
> 收件人: "Christian Benvenuti (benve)" <benve@...co.com>, "davem@...emloft.net" <davem@...emloft.net>, "kuba@...nel.org" <kuba@...nel.org>, "lyl2019@...l.ustc.edu.cn" <lyl2019@...l.ustc.edu.cn>
> 抄送: "netdev@...r.kernel.org" <netdev@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Govindarajulu
>  Varadarajan (gvaradar)" <gvaradar@...co.com>
> 主题: Re: [PATCH] ethernet:enic: Fix a use after free bug in enic_hard_start_xmit
> 
> On Sat, 2021-05-01 at 08:31 -0700, Lv Yunlong wrote:
> > In enic_hard_start_xmit, it calls enic_queue_wq_skb(). Inside
> > enic_queue_wq_skb, if some error happens, the skb will be freed
> > by dev_kfree_skb(skb). But the freed skb is still used in
> > skb_tx_timestamp(skb).
> > 
> > My patch makes enic_queue_wq_skb() return error and goto spin_unlock()
> > incase of error. The solution is provided by Govind.
> > See https://lkml.org/lkml/2021/4/30/961.
> > 
> > Fixes: fb7516d42478e ("enic: add sw timestamp support")
> > Signed-off-by: Lv Yunlong <lyl2019@...l.ustc.edu.cn>
> > ---
> >  drivers/net/ethernet/cisco/enic/enic_main.c | 8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/cisco/enic/enic_main.c
> > b/drivers/net/ethernet/cisco/enic/enic_main.c
> > index f04ec53544ae..40abc3fdeba6 100644
> > --- a/drivers/net/ethernet/cisco/enic/enic_main.c
> > +++ b/drivers/net/ethernet/cisco/enic/enic_main.c
> > @@ -768,7 +768,7 @@ static inline int enic_queue_wq_skb_encap(struct enic
> > *enic, struct vnic_wq *wq,
> >         return err;
> >  }
> >  
> > -static inline void enic_queue_wq_skb(struct enic *enic,
> > +static inline int enic_queue_wq_skb(struct enic *enic,
> >         struct vnic_wq *wq, struct sk_buff *skb)
> >  {
> >         unsigned int mss = skb_shinfo(skb)->gso_size;
> > @@ -813,7 +813,9 @@ static inline void enic_queue_wq_skb(struct enic *enic,
> >                 }
> >                 wq->to_use = buf->next;
> >                 dev_kfree_skb(skb);
> > +               return err;
> 
> return err seems unnecessary here.
> 
> >         }
> > +       return err;
> >  }
> >  
> >  /* netif_tx_lock held, process context with BHs disabled, or BH */
> > @@ -857,7 +859,8 @@ static netdev_tx_t enic_hard_start_xmit(struct sk_buff
> > *skb,
> >                 return NETDEV_TX_BUSY;
> >         }
> >  
> > -       enic_queue_wq_skb(enic, wq, skb);
> > +       if (enic_queue_wq_skb(enic, wq, skb) < 0)
> 
> 0 is success, any other value is error. if (enic_queue_wq_skb(enic, wq, skb)).
> 
> Otherwise patch looks good.
> 
> Thanks
> Govind


Thank you. I have corrected my patch.
See https://lore.kernel.org/patchwork/patch/1420731/.