idpf: cleanup remaining SKBs in PTP flows

When the driver requests Tx timestamp value, one of the first steps is
to clone SKB using skb_get. It increases the reference counter for that
SKB to prevent unexpected freeing by another component.
However, there may be a case where the index is requested, SKB is
assigned and never consumed by PTP flows - for example due to reset during
running PTP apps.

Add a check in release timestamping function to verify if the SKB
assigned to Tx timestamp latch was freed, and release remaining SKBs.

Fixes: 4901e83 ("idpf: add Tx timestamp capabilities negotiation")
Signed-off-by: Milena Olech <milena.olech@intel.com>
Signed-off-by: Anton Nadezhdin <anton.nadezhdin@intel.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Tested-by: Samuel Salin <Samuel.salin@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20251009-jk-iwl-net-2025-10-01-v3-1-ef32a425b92a@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: mwolech

drivers/net/ethernet/intel/idpf/idpf_ptp.c

@@ -863,6 +863,9 @@ static void idpf_ptp_release_vport_tstamp(struct idpf_vport *vport)
 		u64_stats_inc(&vport->tstamp_stats.flushed);
 
 		list_del(&ptp_tx_tstamp->list_member);
+		if (ptp_tx_tstamp->skb)
+			consume_skb(ptp_tx_tstamp->skb);
+
 		kfree(ptp_tx_tstamp);
 	}
 	u64_stats_update_end(&vport->tstamp_stats.stats_sync);

drivers/net/ethernet/intel/idpf/idpf_virtchnl_ptp.c

@@ -517,6 +517,7 @@ idpf_ptp_get_tstamp_value(struct idpf_vport *vport,
 	shhwtstamps.hwtstamp = ns_to_ktime(tstamp);
 	skb_tstamp_tx(ptp_tx_tstamp->skb, &shhwtstamps);
 	consume_skb(ptp_tx_tstamp->skb);
+	ptp_tx_tstamp->skb = NULL;
 
 	list_add(&ptp_tx_tstamp->list_member,
 		 &tx_tstamp_caps->latches_free);