[PATCH v2 1/3] s390/ctcm: Fix return type of ctc{mp,}m_tx()

Nathan Chancellor
2022-11-03T17:01:52Z

drivers/s390/net/ctcm_main.c:1064:21: error: incompatible function pointer types initializing 'netdev_tx_t (*)(struct sk_buff *, struct net_device *)' (aka 'enum netdev_tx (*)(struct sk_buff *, struct net_device *)') with an expression of type 'int (struct sk_buff *, struct net_device *)' [-Werror,-Wincompatible-function-pointer-types-strict]
.ndo_start_xmit = ctcm_tx,
^~~~~~~
drivers/s390/net/ctcm_main.c:1072:21: error: incompatible function pointer types initializing 'netdev_tx_t (*)(struct sk_buff *, struct net_device *)' (aka 'enum netdev_tx (*)(struct sk_buff *, struct net_device *)') with an expression of type 'int (struct sk_buff *, struct net_device *)' [-Werror,-Wincompatible-function-pointer-types-strict]
.ndo_start_xmit = ctcmpc_tx,
^~~~~~~~~

->ndo_start_xmit() in 'struct net_device_ops' expects a return type of
'netdev_tx_t', not 'int'. Adjust the return type of ctc{mp,}m_tx() to
match the prototype's to resolve the warning and potential CFI failure,
should s390 select ARCH_SUPPORTS_CFI_CLANG in the future.

Additionally, while in the area, remove a comment block that is no
longer relevant.

Link: https://github.com/ClangBuiltLinux/linux/issues/1750
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
v2:
- Pick up tags from Alexandra and Kees.
- Remove comment block above ctcm_tx() (Alexandra).
v1: https://lore.kernel.org/20221102163252.49175-1-nathan@kernel.org/
---
drivers/s390/net/ctcm_main.c | 11 ++---------
1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/drivers/s390/net/ctcm_main.c b/drivers/s390/net/ctcm_main.c
index 37b551bd43bf..bdfab9ea0046 100644
--- a/drivers/s390/net/ctcm_main.c
+++ b/drivers/s390/net/ctcm_main.c
@@ -825,16 +825,9 @@ static int ctcmpc_transmit_skb(struct channel *ch, struct sk_buff *skb)
/*
* Start transmission of a packet.
* Called from generic network device layer.
- *
- * skb Pointer to buffer containing the packet.
- * dev Pointer to interface struct.
- *
- * returns 0 if packet consumed, !0 if packet rejected.
- * Note: If we return !0, then the packet is free'd by
- * the generic network layer.
*/
/* first merge version - leaving both functions separated */
-static int ctcm_tx(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t ctcm_tx(struct sk_buff *skb, struct net_device *dev)
{
struct ctcm_priv *priv = dev->ml_priv;

@@ -877,7 +870,7 @@ static int ctcm_tx(struct sk_buff *skb, struct net_device *dev)
}

/* unmerged MPC variant of ctcm_tx */
-static int ctcmpc_tx(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t ctcmpc_tx(struct sk_buff *skb, struct net_device *dev)
{
int len = 0;
struct ctcm_priv *priv = dev->ml_priv;

base-commit: 9abf2313adc1ca1b6180c508c25f22f9395cc780
--
2.38.1