From: Nathan Chancellor <natechancellor@xxxxxxxxx>
Date: Tue, 28 Apr 2020 10:54:56 -0700
> netvsc_start_xmit is used as a callback function for the ndo_start_xmit
> function pointer. ndo_start_xmit's return type is netdev_tx_t but
> netvsc_start_xmit's return type is int.
>
> This causes a failure with Control Flow Integrity (CFI), which requires
> function pointer prototypes and callback function definitions to match
> exactly. When CFI is in enforcing, the kernel panics. When booting a
> CFI kernel with WSL 2, the VM is immediately terminated because of this.
>
> The splat when CONFIG_CFI_PERMISSIVE is used:
...
> Avoid this by using the right return type for netvsc_start_xmit.
>
> Fixes: fceaf24a943d8 ("Staging: hv: add the Hyper-V virtual network driver")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1009
> Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Applied.
