> -----Original Message-----
> From: Magnus Karlsson <[email protected]>
> Sent: Thursday, October 29, 2026 11:02 AM
> To: Karlsson, Magnus <[email protected]>; intel-wired-
> [email protected]; Nguyen, Anthony L <[email protected]>;
> Fijalkowski, Maciej <[email protected]>; Kitszel, Przemyslaw
> <[email protected]>
> Cc: Eric Dumazet <[email protected]>
> Subject: [PATCH iwl-net 2/2] iavf: fix USO for 32-bit systems
>
> That USO works for 64-bit systems is just pure luck. Currently, the
> computation of the UDP segmentation header is performed using sizeof() a
> pointer instead of the sizeof() the UDP header that the pointer points
> to. Since the UDP header happens to be 8 bytes long and a pointer is 8
> bytes long on a 64-bit system, this works on all those systems. But no
> such luck for anyone using a 32-bit system as 8 bytes != 4 bytes. So fix
> this by using sizeof() the UDP header that the pointer points to
> instead.
>
> This was found by an LLM while implementing something else that used
> USO.
>
> Fixes: c91a4f9feb67 ("iavf: add support for UDP Segmentation Offload")
> Reviewed-by: Eric Dumazet <[email protected]>
> Reviewed-by: Maciej Fijalkowski <[email protected]>
> Signed-off-by: Magnus Karlsson <[email protected]>
> ---
> drivers/net/ethernet/intel/iavf/iavf_txrx.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/intel/iavf/iavf_txrx.c
> b/drivers/net/ethernet/intel/iavf/iavf_txrx.c
> index 8982cf75466f..2c290d7788d2 100644
> --- a/drivers/net/ethernet/intel/iavf/iavf_txrx.c
> +++ b/drivers/net/ethernet/intel/iavf/iavf_txrx.c
> @@ -1807,7 +1807,7 @@ static int iavf_tso(struct iavf_tx_buffer *first,
> u8 *hdr_len,
> csum_replace_by_diff(&l4.udp->check,
> (__force __wsum)htonl(paylen));
> /* compute length of UDP segmentation header */
> - *hdr_len = (u8)sizeof(l4.udp) + l4_offset;
> + *hdr_len = sizeof(*l4.udp) + l4_offset;
> } else {
> csum_replace_by_diff(&l4.tcp->check,
> (__force __wsum)htonl(paylen));
> --
> 2.38.1
Reviewed-by: Aleksandr Loktionov <[email protected]>
