Re: [PATCH] can: rockchip_canfd: fix return type of rkcanfd_start_xmit()

[Simon Horman <horms@kernel.org>]

On Fri, Sep 06, 2024 at 01:26:41PM -0700, Nathan Chancellor wrote:
> 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
> warning in clang aims to catch these at compile time, which reveals:
> 
>   drivers/net/can/rockchip/rockchip_canfd-core.c:770:20: 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]
>     770 |         .ndo_start_xmit = rkcanfd_start_xmit,
>         |                           ^~~~~~~~~~~~~~~~~~
> 
> ->ndo_start_xmit() in 'struct net_device_ops' expects a return type of
> 'netdev_tx_t', not 'int' (although the types are ABI compatible). Adjust
> the return type of rkcanfd_start_xmit() to match the prototype's to
> resolve the warning.
> 
> Fixes: ff60bfbaf67f ("can: rockchip_canfd: add driver for Rockchip CAN-FD controller")
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Thanks, I was able to reproduce this problem at build time
and that your patch addresses it.

Reviewed-by: Simon Horman <horms@kernel.org>