The ndo_start_xmit field in net_device_ops is expected to be of type
netdev_tx_t (*ndo_start_xmit)(struct sk_buff *skb, struct net_device *dev).

The mismatched return type breaks forward edge kCFI since the underlying
function definition does not match the function hook definition.

The return type of rtw_xmit_entry should be changed from int to
netdev_tx_t.

Reported-by: Dan Carpenter <error27@gmail.com>
Link: https://github.com/ClangBuiltLinux/linux/issues/1703
Cc: llvm@lists.linux.dev
Signed-off-by: Nathan Huckleberry <nhuck@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
---

Changes v1 -> v2:
- Rebased onto linux-next/master

Changes v2 -> v3:
- Updated header file
- Add reviewed-by tag

 drivers/staging/r8188eu/core/rtw_xmit.c    | 4 ++--
 drivers/staging/r8188eu/include/rtw_xmit.h | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/r8188eu/core/rtw_xmit.c b/drivers/staging/r8188eu/core/rtw_xmit.c
index 98864fc55b25..ea13f11b231b 100644
--- a/drivers/staging/r8188eu/core/rtw_xmit.c
+++ b/drivers/staging/r8188eu/core/rtw_xmit.c
@@ -2289,7 +2289,7 @@ static int rtw_mlcst2unicst(struct adapter *padapter, struct sk_buff *skb)
 	return true;
 }
 
-int rtw_xmit_entry(struct sk_buff *pkt, struct net_device *pnetdev)
+netdev_tx_t rtw_xmit_entry(struct sk_buff *pkt, struct net_device *pnetdev)
 {
 	struct adapter *padapter = (struct adapter *)rtw_netdev_priv(pnetdev);
 	struct xmit_priv *pxmitpriv = &padapter->xmitpriv;
@@ -2323,5 +2323,5 @@ int rtw_xmit_entry(struct sk_buff *pkt, struct net_device *pnetdev)
 	dev_kfree_skb_any(pkt);
 
 exit:
-	return 0;
+	return NETDEV_TX_OK;
 }
diff --git a/drivers/staging/r8188eu/include/rtw_xmit.h b/drivers/staging/r8188eu/include/rtw_xmit.h
index 8f54c41ba927..82efcd54af3f 100644
--- a/drivers/staging/r8188eu/include/rtw_xmit.h
+++ b/drivers/staging/r8188eu/include/rtw_xmit.h
@@ -368,6 +368,6 @@ int rtw_ack_tx_wait(struct xmit_priv *pxmitpriv, u32 timeout_ms);
 void rtw_ack_tx_done(struct xmit_priv *pxmitpriv, int status);
 
 void rtw_xmit_complete(struct adapter *padapter, struct xmit_frame *pxframe);
-int rtw_xmit_entry(struct sk_buff *pkt, struct net_device *pnetdev);
+netdev_tx_t rtw_xmit_entry(struct sk_buff *pkt, struct net_device *pnetdev);
 
 #endif	/* _RTL871X_XMIT_H_ */
-- 
2.37.2.789.g6183377224-goog

On 9/14/22 23:16, Nathan Huckleberry wrote:
> The ndo_start_xmit field in net_device_ops is expected to be of type
> netdev_tx_t (*ndo_start_xmit)(struct sk_buff *skb, struct net_device *dev).
> 
> The mismatched return type breaks forward edge kCFI since the underlying
> function definition does not match the function hook definition.
> 
> The return type of rtw_xmit_entry should be changed from int to
> netdev_tx_t.
> 
> Reported-by: Dan Carpenter <error27@gmail.com>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1703
> Cc: llvm@lists.linux.dev
> Signed-off-by: Nathan Huckleberry <nhuck@google.com>
> Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> ---
> 
> Changes v1 -> v2:
> - Rebased onto linux-next/master
> 
> Changes v2 -> v3:
> - Updated header file
> - Add reviewed-by tag
> 
>   drivers/staging/r8188eu/core/rtw_xmit.c    | 4 ++--
>   drivers/staging/r8188eu/include/rtw_xmit.h | 2 +-
>   2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/r8188eu/core/rtw_xmit.c b/drivers/staging/r8188eu/core/rtw_xmit.c
> index 98864fc55b25..ea13f11b231b 100644
> --- a/drivers/staging/r8188eu/core/rtw_xmit.c
> +++ b/drivers/staging/r8188eu/core/rtw_xmit.c
> @@ -2289,7 +2289,7 @@ static int rtw_mlcst2unicst(struct adapter *padapter, struct sk_buff *skb)
>   	return true;
>   }
>   
> -int rtw_xmit_entry(struct sk_buff *pkt, struct net_device *pnetdev)
> +netdev_tx_t rtw_xmit_entry(struct sk_buff *pkt, struct net_device *pnetdev)
>   {
>   	struct adapter *padapter = (struct adapter *)rtw_netdev_priv(pnetdev);
>   	struct xmit_priv *pxmitpriv = &padapter->xmitpriv;
> @@ -2323,5 +2323,5 @@ int rtw_xmit_entry(struct sk_buff *pkt, struct net_device *pnetdev)
>   	dev_kfree_skb_any(pkt);
>   
>   exit:
> -	return 0;
> +	return NETDEV_TX_OK;
>   }
> diff --git a/drivers/staging/r8188eu/include/rtw_xmit.h b/drivers/staging/r8188eu/include/rtw_xmit.h
> index 8f54c41ba927..82efcd54af3f 100644
> --- a/drivers/staging/r8188eu/include/rtw_xmit.h
> +++ b/drivers/staging/r8188eu/include/rtw_xmit.h
> @@ -368,6 +368,6 @@ int rtw_ack_tx_wait(struct xmit_priv *pxmitpriv, u32 timeout_ms);
>   void rtw_ack_tx_done(struct xmit_priv *pxmitpriv, int status);
>   
>   void rtw_xmit_complete(struct adapter *padapter, struct xmit_frame *pxframe);
> -int rtw_xmit_entry(struct sk_buff *pkt, struct net_device *pnetdev);
> +netdev_tx_t rtw_xmit_entry(struct sk_buff *pkt, struct net_device *pnetdev);
>   
>   #endif	/* _RTL871X_XMIT_H_ */

Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150