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

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 <redacted>
---
 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

On Sat, 2021-05-01 at 08:31 -0700, Lv Yunlong wrote:

return err seems unnecessary here.

0 is success, any other value is error. if (enic_queue_wq_skb(enic, wq, skb)).

Otherwise patch looks good.

Thanks
Govind

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

quoted

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 <redacted>
---
 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.

quoted

        }
+       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/.