[PATCH iwl-net v2 5/5] i40e: fix races in PTP external timestamp work handling

From: Xuanqiang Luo <[email protected]>

The time sync interrupt queues ptp_extts0_work, which reads device
registers and reports events through pf->ptp_clock. i40e_ptp_stop()
unregisters the PHC before disabling the event source or draining the
work. The worker can therefore use the clock or PF after either has been
freed.

Move the event-source shutdown before PHC unregister. i40e_ptp_stop()
first clears I40E_FLAG_PTP_ENA under ptp_config_lock, so timestamp
configuration cannot re-enable the source after the lock is released.
Then call disable_work_sync() to reject later queue attempts and drain
work already pending or running.

INIT_WORK() is currently called from i40e_ptp_set_timestamp_mode(), which
runs on reset and whenever timestamping is reconfigured. Reinitializing
pending or running work can corrupt its workqueue state. Initialize the
work once from i40e_sw_init() instead.

Fixes: 1050713026a0 ("i40e: add support for PTP external synchronization clock")
Signed-off-by: Xuanqiang Luo <[email protected]>
---
 drivers/net/ethernet/intel/i40e/i40e.h      |  1 +
 drivers/net/ethernet/intel/i40e/i40e_main.c |  1 +
 drivers/net/ethernet/intel/i40e/i40e_ptp.c  | 25 +++++++++++++++------
 3 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e.h b/drivers/net/ethernet/intel/i40e/i40e.h
index 84564d747d09a..18452f9aa74e1 100644
--- a/drivers/net/ethernet/intel/i40e/i40e.h
+++ b/drivers/net/ethernet/intel/i40e/i40e.h
@@ -1318,6 +1318,7 @@ int i40e_ptp_hwtstamp_set(struct net_device *netdev,
 			  struct netlink_ext_ack *extack);
 void i40e_ptp_save_hw_time(struct i40e_pf *pf);
 void i40e_ptp_restore_hw_time(struct i40e_pf *pf);
+void i40e_ptp_init_work(struct i40e_pf *pf);
 void i40e_ptp_init(struct i40e_pf *pf);
 void i40e_ptp_stop(struct i40e_pf *pf);
 int i40e_ptp_alloc_pins(struct i40e_pf *pf);
diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
index c19d4c81d6532..48ba38a452d0b 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_main.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
@@ -12822,6 +12822,7 @@ static int i40e_sw_init(struct i40e_pf *pf)
 	}
 	mutex_init(&pf->switch_mutex);
 	mutex_init(&pf->ptp_config_lock);
+	i40e_ptp_init_work(pf);
 	spin_lock_init(&pf->ptp_tx_lock);
 
 sw_init_done:
diff --git a/drivers/net/ethernet/intel/i40e/i40e_ptp.c b/drivers/net/ethernet/intel/i40e/i40e_ptp.c
index f194869947124..5f15a3d4a91ed 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_ptp.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_ptp.c
@@ -169,6 +169,17 @@ static void i40e_ptp_extts0_work(struct work_struct *work)
 	ptp_clock_event(pf->ptp_clock, &event);
 }
 
+/**
+ * i40e_ptp_init_work - Initialize PTP work for a PF
+ * @pf: Board private structure
+ *
+ * Initialize work which must remain valid for the lifetime of the PF.
+ */
+void i40e_ptp_init_work(struct i40e_pf *pf)
+{
+	INIT_WORK(&pf->ptp_extts0_work, i40e_ptp_extts0_work);
+}
+
 /**
  * i40e_is_ptp_pin_dev - check if device supports PTP pins
  * @hw: pointer to the hardware structure
@@ -1201,8 +1212,6 @@ static int i40e_ptp_set_timestamp_mode(struct i40e_pf *pf,
 	regval |= 1 << I40E_PRTTSYN_CTL0_EVENT_INT_ENA_SHIFT;
 	wr32(hw, I40E_PRTTSYN_CTL0, regval);
 
-	INIT_WORK(&pf->ptp_extts0_work, i40e_ptp_extts0_work);
-
 	switch (config->tx_type) {
 	case HWTSTAMP_TX_OFF:
 		pf->ptp_tx = false;
@@ -1576,6 +1585,13 @@ void i40e_ptp_stop(struct i40e_pf *pf)
 	pf->ptp_rx = false;
 	mutex_unlock(&pf->ptp_config_lock);
 
+	/* Stop external timestamp events before unregistering the clock. */
+	regval = rd32(hw, I40E_PRTTSYN_CTL0);
+	regval &= ~I40E_PRTTSYN_CTL0_EVENT_INT_ENA_MASK;
+	wr32(hw, I40E_PRTTSYN_CTL0, regval);
+
+	disable_work_sync(&pf->ptp_extts0_work);
+
 	if (skb)
 		dev_kfree_skb_any(skb);
 
@@ -1596,10 +1612,5 @@ void i40e_ptp_stop(struct i40e_pf *pf)
 	regval &= ~I40E_PRTTSYN_AUX_0_PTPFLAG_MASK;
 	wr32(hw, I40E_PRTTSYN_AUX_0(0), regval);
 
-	/* Disable interrupts */
-	regval = rd32(hw, I40E_PRTTSYN_CTL0);
-	regval &= ~I40E_PRTTSYN_CTL0_EVENT_INT_ENA_MASK;
-	wr32(hw, I40E_PRTTSYN_CTL0, regval);
-
 	i40e_ptp_free_pins(pf);
 }
-- 
2.43.0