ice: Don't process extts if PTP is disabled

The ice_ptp_extts_event() function can race with ice_ptp_release() and
result in a NULL pointer dereference which leads to a kernel panic.

Panic occurs because the ice_ptp_extts_event() function calls
ptp_clock_event() with a NULL pointer. The ice driver has already
released the PTP clock by the time the interrupt for the next external
timestamp event occurs.

To fix this, modify the ice_ptp_extts_event() function to check the
PTP state and bail early if PTP is not ready.

Fixes: 172db5f ("ice: add support for auxiliary input/output pins")
Reviewed-by: Przemek Kitszel <[email protected]>
Signed-off-by: Jacob Keller <[email protected]>
Signed-off-by: Karol Kolacinski <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Tested-by: Pucha Himasekhar Reddy <[email protected]> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: jacob-keller

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

@@ -1559,6 +1559,10 @@ void ice_ptp_extts_event(struct ice_pf *pf)
 	u8 chan, tmr_idx;
 	u32 hi, lo;
 
+	/* Don't process timestamp events if PTP is not ready */
+	if (pf->ptp.state != ICE_PTP_READY)
+		return;
+
 	tmr_idx = hw->func_caps.ts_func_info.tmr_index_owned;
 	/* Event time is captured by one of the two matched registers
 	 *      GLTSYN_EVNT_L: 32 LSB of sampled time event