[PATCH v2 3/3] s390/lcs: Fix return type of lcs_start_xmit()

Nathan Chancellor
2022-11-03T17:01:55Z

drivers/s390/net/lcs.c:2090:21: 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 = lcs_start_xmit,
^~~~~~~~~~~~~~
drivers/s390/net/lcs.c:2097:21: 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 = lcs_start_xmit,
^~~~~~~~~~~~~~

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

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.
- Adjust indentation of modified lines, as they can fit within the
line limit (Alexandra).
v1: https://lore.kernel.org/20221102163252.49175-3-nathan@kernel.org/
---
drivers/s390/net/lcs.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/s390/net/lcs.c b/drivers/s390/net/lcs.c
index 84c8981317b4..38f312664ce7 100644
--- a/drivers/s390/net/lcs.c
+++ b/drivers/s390/net/lcs.c
@@ -1519,9 +1519,8 @@ lcs_txbuffer_cb(struct lcs_channel *channel, struct lcs_buffer *buffer)
/*
* Packet transmit function called by network stack
*/
-static int
-__lcs_start_xmit(struct lcs_card *card, struct sk_buff *skb,
- struct net_device *dev)
+static netdev_tx_t __lcs_start_xmit(struct lcs_card *card, struct sk_buff *skb,
+ struct net_device *dev)
{
struct lcs_header *header;
int rc = NETDEV_TX_OK;
@@ -1582,8 +1581,7 @@ __lcs_start_xmit(struct lcs_card *card, struct sk_buff *skb,
return rc;
}

-static int
-lcs_start_xmit(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t lcs_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
struct lcs_card *card;
int rc;
--
2.38.1