Re: [PATCH net] net: ethtool: fix wrong type used in struct kernel_ethtool_ts_info

[Jakub Kicinski <kuba@kernel.org>]

On Sun, 07 Sep 2025 21:43:20 +0100 Russell King (Oracle) wrote:
> In C, enumerated types do not have a defined size, apart from being
> compatible with one of the standard types. This allows an ABI /
> compiler to choose the type of an enum depending on the values it
> needs to store, and storing larger values in it can lead to undefined
> behaviour.
> 
> The tx_type and rx_filters members of struct kernel_ethtool_ts_info
> are defined as enumerated types, but are bit arrays, where each bit
> is defined by the enumerated type. This means they typically store
> values in excess of the maximum value of the enumerated type, in
> fact (1 << max_value) and thus must not be declared using the
> enumated type.
> 
> Fix both of these to use u32, as per the corresponding __u32 UAPI type.
> 
> Fixes: 2111375b85ad ("net: Add struct kernel_ethtool_ts_info")

Do you feel strongly about this being a fix? (I can adjust when
applying FWIW). It's clearly not great but I don't think storing
a mask of enum values cause functional problems.