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From: Nathan Chancellor <>
To: Thomas Sailer <>,
	"David S. Miller" <>,
	Eric Dumazet <>,
	Jakub Kicinski <>, Paolo Abeni <>
	Nick Desaulniers <>,
	Tom Rix <>, Kees Cook <>,
	Sami Tolvanen <>,,,, Nathan Chancellor <>
Subject: [PATCH] hamradio: baycom_epp: Fix return type of baycom_send_packet()
Date: Wed,  2 Nov 2022 09:06:10 -0700	[thread overview]
Message-ID: <> (raw)

With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG),
indirect call targets are validated against the expected function
pointer prototype to make sure the call target is valid to help mitigate
ROP attacks. If they are not identical, there is a failure at run time,
which manifests as either a kernel panic or thread getting killed. A
proposed warning in clang aims to catch these at compile time, which

  drivers/net/hamradio/baycom_epp.c:1119:25: 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      = baycom_send_packet,
  1 error generated.

->ndo_start_xmit() in 'struct net_device_ops' expects a return type of
'netdev_tx_t', not 'int'. Adjust the return type of baycom_send_packet()
to match the prototype's to resolve the warning and CFI failure.

Signed-off-by: Nathan Chancellor <>
 drivers/net/hamradio/baycom_epp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/hamradio/baycom_epp.c b/drivers/net/hamradio/baycom_epp.c
index 791b4a53d69f..bd3b0c2655a2 100644
--- a/drivers/net/hamradio/baycom_epp.c
+++ b/drivers/net/hamradio/baycom_epp.c
@@ -758,7 +758,7 @@ static void epp_bh(struct work_struct *work)
  * ===================== network driver interface =========================
-static int baycom_send_packet(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t baycom_send_packet(struct sk_buff *skb, struct net_device *dev)
 	struct baycom_state *bc = netdev_priv(dev);

base-commit: 9abf2313adc1ca1b6180c508c25f22f9395cc780

             reply	other threads:[~2022-11-02 16:06 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-02 16:06 Nathan Chancellor [this message]
2022-11-02 19:08 ` [PATCH] hamradio: baycom_epp: Fix return type of baycom_send_packet() Kees Cook
2022-11-04  5:00 ` patchwork-bot+netdevbpf

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