Re: [PATCH iwl-net 2/2] iavf: fix USO for 32-bit systems

On Tue, 27 Oct 2026 at 14:43, Eric Dumazet [off-list ref] wrote:

Le mar. 27 oct. 2026 à 13:15, Magnus Karlsson
[off-list ref] a écrit :

quoted

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: c91a4f9feb67a199c2 ("add support for UDP Segmentation Offload")

Missing prefix? This was really:

Fixes: c91a4f9feb67 ("iavf: add support for UDP Segmentation Offload")

You are correct on both accounts/patches. Do not know why I missed this, sorry.

Do you want a v2 with this added?

Other than this,
Reviewed-by: Eric Dumazet <edumazet@kernel.org>

quoted

Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
---
 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