Re: [PATCH net 2/3] igc: prepare TSO and checksum offloads before TX timestamps

[Eric Dumazet]

Le lun. 26 oct. 2026 à 10:16, Paul Moses <p@xxxxxxx> a écrit :
>
> igc_request_tx_tstamp() takes an extra skb reference before transmit
> preparation. For GSO packets, igc_tso() calls skb_cow_head(), which can
> reach pskb_expand_head() with a shared skb when the header is cloned.
> Commit c7d8bc3dd511 ("net: skbuff: don't BUG() on bad arguments to
> pskb_expand_head()") replaced the BUG_ON() with -EINVAL, causing TSO
> preparation to fail and the packet to be dropped.
>
> For non-GSO packets with CHECKSUM_PARTIAL, igc_tx_csum() falls back to
> skb_checksum_help() for unsupported checksum offsets. This can also
> reach pskb_expand_head() through skb_ensure_writable(). igc_tx_csum()
> ignores the error, allowing transmission to continue without completing
> the checksum.
>
> Move TSO and checksum preparation before TX timestamp reservation so
> the extra skb reference cannot interfere with either operation.
>
> Fixes: 2c344ae24501 ("igc: Add support for TX timestamping")
> Fixes: f38b782dccab ("igc: Add support for TSO")
> Signed-off-by: Paul Moses <p@xxxxxxx>
> ---

Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>