idpf: fix potential use-after-free in idpf_tso()

idpf: fix potential use-after-free in idpf_tso()

skb_cow_head() can change skb->head (and thus skb_shinfo(skb))

We must not cache skb_shinfo(skb) before skb_cow_head().

Fixes: 6818c4d5b3c2 ("idpf: add splitq start_xmit")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Joshua Hay <joshua.a.hay@intel.com>
Cc: Alan Brady <alan.brady@intel.com>
Cc: Madhu Chittim <madhu.chittim@intel.com>
Cc: Phani Burra <phani.r.burra@intel.com>
Cc: Sridhar Samudrala <sridhar.samudrala@intel.com>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Pavan Kumar Linga <pavan.kumar.linga@intel.com>
Cc: Tony Nguyen <anthony.l.nguyen@intel.com>
Cc: Bailey Forrest <bcf@google.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://lore.kernel.org/r/20231103200451.514047-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>