Re: [PATCH net 1/8] net: bcmgenet: fix 64-bit RTNL stats reading in ethtool on 32-bit systems

[Nicolai Buchwitz <nb@tipi-net.de>]

On 18.9.2026 02:07, Florian Fainelli wrote:
> When bcmgenet was converted to 64-bit statistics, STAT_RTNL members 
> were
> switched to point into struct rtnl_link_stats64, whose fields are 
> 64-bit
> (__u64) regardless of architecture.
> 
> However, bcmgenet_get_ethtool_stats() retained a legacy check:
>   if (sizeof(unsigned long) != sizeof(u32) &&
>       s->stat_sizeof == sizeof(unsigned long))
> 
> On 32-bit systems, sizeof(unsigned long) == sizeof(u32), causing this
> condition to evaluate to false. As a result, 64-bit RTNL stats fields 
> were
> read via *(u32 *)p. On 32-bit Big-Endian systems (such as MIPS BE), 
> this
> reads the high 32 bits and returns 0 until the counter exceeds 4GB; on
> 32-bit Little-Endian systems (such as 32-bit ARM), the value is 
> truncated
> to 32 bits.
> 
> Fix this by checking if s->stat_sizeof == sizeof(u64) so 64-bit fields 
> are
> always read as 64-bit values.
> 
> Fixes: 59aa6e3072aa ("net: bcmgenet: switch to use 64bit statistics")
> Assisted-by: LLM
> Co-authored-by: Cursor <cursoragent@cursor.com>
> Change-Id: I3e9f2f8d4fd136392148d6c0cd4eb40f7ccbe4ef
> ---
>  drivers/net/ethernet/broadcom/genet/bcmgenet.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c 
> b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> index b916080f4ff1..7b089de9484e 100644
> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> @@ -1346,9 +1346,8 @@ static void bcmgenet_get_ethtool_stats(struct 
> net_device *dev,
>  				p = (char *)&stats64;
> 
>  			p += s->stat_offset;
> -			if (sizeof(unsigned long) != sizeof(u32) &&
> -				s->stat_sizeof == sizeof(unsigned long))
> -				data[i] = *(unsigned long *)p;
> +			if (s->stat_sizeof == sizeof(u64))
> +				data[i] = *(u64 *)p;
>  			else
>  				data[i] = *(u32 *)p;
>  		}

Reviewed-by: Nicolai Buchwitz <nb@tipi-net.de>

Thanks,
Nicolai