[PATCH] ethernet:enic: Fix a use after free bug in enic_hard_start_xmit

[PATCH] ethernet:enic: Fix a use after free bug in enic_hard_start_xmit

[Lv Yunlong]

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@mail.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;
 }
 
 /* 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)
+		goto error;
 
 	if (vnic_wq_desc_avail(wq) < MAX_SKB_FRAGS + ENIC_DESC_MAX_SPLITS)
 		netif_tx_stop_queue(txq);
@@ -865,6 +868,7 @@ static netdev_tx_t enic_hard_start_xmit(struct sk_buff *skb,
 	if (!netdev_xmit_more() || netif_xmit_stopped(txq))
 		vnic_wq_doorbell(wq);
 
+error:
 	spin_unlock(&enic->wq_lock[txq_map]);
 
 	return NETDEV_TX_OK;
-- 
2.25.1

Re: [PATCH] ethernet:enic: Fix a use after free bug in enic_hard_start_xmit

[Govindarajulu Varadarajan (gvaradar)]

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@mail.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

Re: Re: [PATCH] ethernet:enic: Fix a use after free bug in enic_hard_start_xmit

[lyl2019]

> -----原始邮件-----
> 发件人: "Govindarajulu Varadarajan (gvaradar)" <gvaradar@cisco.com>
> 发送时间: 2021-05-02 09:12:49 (星期日)
> 收件人: "Christian Benvenuti (benve)" <benve@cisco.com>, "davem@davemloft.net" <davem@davemloft.net>, "kuba@kernel.org" <kuba@kernel.org>, "lyl2019@mail.ustc.edu.cn" <lyl2019@mail.ustc.edu.cn>
> 抄送: "netdev@vger.kernel.org" <netdev@vger.kernel.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "Govindarajulu
>  Varadarajan (gvaradar)" <gvaradar@cisco.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@mail.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/.