ice: fix NULL access of tx->in_use in ice_ptp_ts_irq

JIRA: https://issues.redhat.com/browse/RHEL-84608

Upstream commit(s):
commit 403bf04
Author: Jacob Keller <jacob.e.keller@intel.com>
Date:   Thu Aug 7 10:35:26 2025 -0700

    ice: fix NULL access of tx->in_use in ice_ptp_ts_irq

    The E810 device has support for a "low latency" firmware interface to
    access and read the Tx timestamps. This interface does not use the standard
    Tx timestamp logic, due to the latency overhead of proxying sideband
    command requests over the firmware AdminQ.

    The logic still makes use of the Tx timestamp tracking structure,
    ice_ptp_tx, as it uses the same "ready" bitmap to track which Tx
    timestamps complete.

    Unfortunately, the ice_ptp_ts_irq() function does not check if the tracker
    is initialized before its first access. This results in NULL dereference or
    use-after-free bugs similar to the following:

    [245977.278756] BUG: kernel NULL pointer dereference, address: 0000000000000000
    [245977.278774] RIP: 0010:_find_first_bit+0x19/0x40
    [245977.278796] Call Trace:
    [245977.278809]  ? ice_misc_intr+0x364/0x380 [ice]

    This can occur if a Tx timestamp interrupt races with the driver reset
    logic.

    Fix this by only checking the in_use bitmap (and other fields) if the
    tracker is marked as initialized. The reset flow will clear the init field
    under lock before it tears the tracker down, thus preventing any
    use-after-free or NULL access.

    Fixes: f9472aa ("ice: Process TSYN IRQ in a separate function")
    Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
    Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>
    Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
    Tested-by: Rinitha S <sx.rinitha@intel.com> (A Contingent worker at Intel)
    Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

Signed-off-by: Petr Oros <poros@redhat.com>

Author: orosp

drivers/net/ethernet/intel/ice/ice_ptp.c

@@ -2882,16 +2882,19 @@ irqreturn_t ice_ptp_ts_irq(struct ice_pf *pf)
 		 */
 		if (hw->dev_caps.ts_dev_info.ts_ll_int_read) {
 			struct ice_ptp_tx *tx = &pf->ptp.port.tx;
-			u8 idx;
+			u8 idx, last;
 
 			if (!ice_pf_state_is_nominal(pf))
 				return IRQ_HANDLED;
 
 			spin_lock(&tx->lock);
-			idx = find_next_bit_wrap(tx->in_use, tx->len,
-						 tx->last_ll_ts_idx_read + 1);
-			if (idx != tx->len)
-				ice_ptp_req_tx_single_tstamp(tx, idx);
+			if (tx->init) {
+				last = tx->last_ll_ts_idx_read + 1;
+				idx = find_next_bit_wrap(tx->in_use, tx->len,
+							 last);
+				if (idx != tx->len)
+					ice_ptp_req_tx_single_tstamp(tx, idx);
+			}
 			spin_unlock(&tx->lock);
 
 			return IRQ_HANDLED;