This is a note to let you know that I've just added the patch titled hamradio: baycom_epp: Fix return type of baycom_send_packet() to the 6.1-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: hamradio-baycom_epp-fix-return-type-of-baycom_send_p.patch and it can be found in the queue-6.1 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 244b2a61119cdf781a5f277cee536ff2f76de180 Author: Nathan Chancellor <nathan@xxxxxxxxxx> Date: Wed Nov 2 09:06:10 2022 -0700 hamradio: baycom_epp: Fix return type of baycom_send_packet() [ Upstream commit c5733e5b15d91ab679646ec3149e192996a27d5d ] 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 reveals: 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. Link: https://github.com/ClangBuiltLinux/linux/issues/1750 Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> Link: https://lore.kernel.org/r/20221102160610.1186145-1-nathan@xxxxxxxxxx Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> 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);