[PATCH v3] net: mana: Fix return type of mana_start_xmit()

Nathan Chancellor
2022-11-09T00:28:52Z

From: Nathan Huckleberry <nhuck@google.com>

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. A new
warning in clang will catch this at compile time:

drivers/net/ethernet/microsoft/mana/mana_en.c:382:21: 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 = mana_start_xmit,
^~~~~~~~~~~~~~~
1 error generated.

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

Reported-by: Dan Carpenter <error27@gmail.com>
Link: https://github.com/ClangBuiltLinux/linux/issues/1703
Link: https://github.com/ClangBuiltLinux/linux/issues/1750
Signed-off-by: Nathan Huckleberry <nhuck@google.com>
Reviewed-by: Dexuan Cui <decui@microsoft.com>
[nathan: Rebase on net-next and resolve conflicts
Add note about new clang warning]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---

v3:
- Take over for Nathan, as he is busy with other matters.
- Rebase on net-next and resolve conflicts.
- Add a note about new clang warning that will catch this issue at
compile time.

v2: https://lore.kernel.org/20220929181411.61331-1-nhuck@google.com/

drivers/net/ethernet/microsoft/mana/mana.h | 2 +-
drivers/net/ethernet/microsoft/mana/mana_en.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/mana.h b/drivers/net/ethernet/microsoft/mana/mana.h
index d58be64374c8..ffcd27cde17b 100644
--- a/drivers/net/ethernet/microsoft/mana/mana.h
+++ b/drivers/net/ethernet/microsoft/mana/mana.h
@@ -388,7 +388,7 @@ struct mana_port_context {
struct mana_ethtool_stats eth_stats;
};

-int mana_start_xmit(struct sk_buff *skb, struct net_device *ndev);
+netdev_tx_t mana_start_xmit(struct sk_buff *skb, struct net_device *ndev);
int mana_config_rss(struct mana_port_context *ac, enum TRI_STATE rx,
bool update_hash, bool update_tab);

diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index 318dbbb48279..91a8d3577c14 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -128,7 +128,7 @@ static int mana_map_skb(struct sk_buff *skb, struct mana_port_context *apc,
return -ENOMEM;
}

-int mana_start_xmit(struct sk_buff *skb, struct net_device *ndev)
+netdev_tx_t mana_start_xmit(struct sk_buff *skb, struct net_device *ndev)
{
enum mana_tx_pkt_format pkt_fmt = MANA_SHORT_PKT_FMT;
struct mana_port_context *apc = netdev_priv(ndev);

base-commit: 8e18be7610aebea50e9327c11afcd5eeaaa06644
--
2.38.1