[PATCH v2] 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 | 7 +++++--
 1 file changed, 5 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..b1443ff439de 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;

@@ -814,6 +814,7 @@ static inline void enic_queue_wq_skb(struct enic *enic,
 		wq->to_use = buf->next;
 		dev_kfree_skb(skb);
 	}
+	return err;
 }
 
 /* netif_tx_lock held, process context with BHs disabled, or BH */

@@ -857,7 +858,8 @@ 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))
+		goto error;
 
 	if (vnic_wq_desc_avail(wq) < MAX_SKB_FRAGS + ENIC_DESC_MAX_SPLITS)
 		netif_tx_stop_queue(txq);

@@ -865,6 +867,7 @@ 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 Sun, 2021-05-02 at 04:58 -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 <redacted>

Thanks,

Acked-by: Govindarajulu Varadarajan <redacted>

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Sun,  2 May 2021 04:58:18 -0700 you 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.

[...]

Here is the summary with links:
  - [v2] ethernet:enic: Fix a use after free bug in enic_hard_start_xmit
    https://git.kernel.org/netdev/net/c/643001b47adc

You are awesome, thank you!
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