ice: fix race condition in TX timestamp ring cleanup

Fix a race condition between ice_free_tx_tstamp_ring() and ice_tx_map()
that can cause a NULL pointer dereference.

ice_free_tx_tstamp_ring currently clears the ICE_TX_FLAGS_TXTIME flag
after NULLing the tstamp_ring. This could allow a concurrent ice_tx_map
call on another CPU to dereference the tstamp_ring, which could lead to
a NULL pointer dereference.

  CPU A:ice_free_tx_tstamp_ring() | CPU B:ice_tx_map()
  --------------------------------|---------------------------------
  tx_ring->tstamp_ring = NULL     |
                                  | ice_is_txtime_cfg() -> true
                                  | tstamp_ring = tx_ring->tstamp_ring
                                  | tstamp_ring->count  // NULL deref!
  flags &= ~ICE_TX_FLAGS_TXTIME   |

Fix by:
1. Reordering ice_free_tx_tstamp_ring() to clear the flag before
   NULLing the pointer, with smp_wmb() to ensure proper ordering.
2. Adding smp_rmb() in ice_tx_map() after the flag check to order the
   flag read before the pointer read, using READ_ONCE() for the
   pointer, and adding a NULL check as a safety net.
3. Converting tx_ring->flags from u8 to DECLARE_BITMAP() and using
   atomic bitops (set_bit(), clear_bit(), test_bit()) for all flag
   operations throughout the driver:
   - ICE_TX_RING_FLAGS_XDP
   - ICE_TX_RING_FLAGS_VLAN_L2TAG1
   - ICE_TX_RING_FLAGS_VLAN_L2TAG2
   - ICE_TX_RING_FLAGS_TXTIME

Fixes: ccde82e909467 ("ice: add E830 Earliest TxTime First Offload support")
Signed-off-by: Keita Morisaki <kmta1236@gmail.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Tested-by: Rinitha S <sx.rinitha@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20260416-iwl-net-submission-2026-04-14-v2-7-686c33c9828d@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

5 files changed, 31 insertions, 18 deletions

diff --git a/drivers/net/ethernet/intel/ice/ice.h b/drivers/net/ethernet/intel/ice/ice.h
index eb3a48330cc1..725b130dd3a2 100644
--- a/drivers/net/ethernet/intel/ice/ice.h
+++ b/drivers/net/ethernet/intel/ice/ice.h
@@ -753,7 +753,7 @@ static inline bool ice_is_xdp_ena_vsi(struct ice_vsi *vsi)
 
 static inline void ice_set_ring_xdp(struct ice_tx_ring *ring)
 {
-	ring->flags |= ICE_TX_FLAGS_RING_XDP;
+	set_bit(ICE_TX_RING_FLAGS_XDP, ring->flags);
 }
 
 /**
@@ -778,7 +778,7 @@ static inline bool ice_is_txtime_ena(const struct ice_tx_ring *ring)
  */
 static inline bool ice_is_txtime_cfg(const struct ice_tx_ring *ring)
 {
-	return !!(ring->flags & ICE_TX_FLAGS_TXTIME);
+	return test_bit(ICE_TX_RING_FLAGS_TXTIME, ring->flags);
 }
 
 /**
diff --git a/drivers/net/ethernet/intel/ice/ice_dcb_lib.c b/drivers/net/ethernet/intel/ice/ice_dcb_lib.c
index bd77f1c001ee..16aa25535152 100644
--- a/drivers/net/ethernet/intel/ice/ice_dcb_lib.c
+++ b/drivers/net/ethernet/intel/ice/ice_dcb_lib.c
@@ -943,7 +943,7 @@ ice_tx_prepare_vlan_flags_dcb(struct ice_tx_ring *tx_ring,
 		/* if this is not already set it means a VLAN 0 + priority needs
 		 * to be offloaded
 		 */
-		if (tx_ring->flags & ICE_TX_FLAGS_RING_VLAN_L2TAG2)
+		if (test_bit(ICE_TX_RING_FLAGS_VLAN_L2TAG2, tx_ring->flags))
 			first->tx_flags |= ICE_TX_FLAGS_HW_OUTER_SINGLE_VLAN;
 		else
 			first->tx_flags |= ICE_TX_FLAGS_HW_VLAN;
diff --git a/drivers/net/ethernet/intel/ice/ice_lib.c b/drivers/net/ethernet/intel/ice/ice_lib.c
index 689c6025ea82..837b71b7b2b7 100644
--- a/drivers/net/ethernet/intel/ice/ice_lib.c
+++ b/drivers/net/ethernet/intel/ice/ice_lib.c
@@ -1412,9 +1412,9 @@ static int ice_vsi_alloc_rings(struct ice_vsi *vsi)
 		ring->count = vsi->num_tx_desc;
 		ring->txq_teid = ICE_INVAL_TEID;
 		if (dvm_ena)
-			ring->flags |= ICE_TX_FLAGS_RING_VLAN_L2TAG2;
+			set_bit(ICE_TX_RING_FLAGS_VLAN_L2TAG2, ring->flags);
 		else
-			ring->flags |= ICE_TX_FLAGS_RING_VLAN_L2TAG1;
+			set_bit(ICE_TX_RING_FLAGS_VLAN_L2TAG1, ring->flags);
 		WRITE_ONCE(vsi->tx_rings[i], ring);
 	}
 
diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.c b/drivers/net/ethernet/intel/ice/ice_txrx.c
index 7be9c062949b..4ca1a0602307 100644
--- a/drivers/net/ethernet/intel/ice/ice_txrx.c
+++ b/drivers/net/ethernet/intel/ice/ice_txrx.c
@@ -190,9 +190,10 @@ void ice_free_tstamp_ring(struct ice_tx_ring *tx_ring)
 void ice_free_tx_tstamp_ring(struct ice_tx_ring *tx_ring)
 {
 	ice_free_tstamp_ring(tx_ring);
+	clear_bit(ICE_TX_RING_FLAGS_TXTIME, tx_ring->flags);
+	smp_wmb();	/* order flag clear before pointer NULL */
 	kfree_rcu(tx_ring->tstamp_ring, rcu);
-	tx_ring->tstamp_ring = NULL;
-	tx_ring->flags &= ~ICE_TX_FLAGS_TXTIME;
+	WRITE_ONCE(tx_ring->tstamp_ring, NULL);
 }
 
 /**
@@ -405,7 +406,7 @@ static int ice_alloc_tstamp_ring(struct ice_tx_ring *tx_ring)
 	tx_ring->tstamp_ring = tstamp_ring;
 	tstamp_ring->desc = NULL;
 	tstamp_ring->count = ice_calc_ts_ring_count(tx_ring);
-	tx_ring->flags |= ICE_TX_FLAGS_TXTIME;
+	set_bit(ICE_TX_RING_FLAGS_TXTIME, tx_ring->flags);
 	return 0;
 }
 
@@ -1521,13 +1522,20 @@ ice_tx_map(struct ice_tx_ring *tx_ring, struct ice_tx_buf *first,
 		return;
 
 	if (ice_is_txtime_cfg(tx_ring)) {
-		struct ice_tstamp_ring *tstamp_ring = tx_ring->tstamp_ring;
-		u32 tstamp_count = tstamp_ring->count;
-		u32 j = tstamp_ring->next_to_use;
+		struct ice_tstamp_ring *tstamp_ring;
+		u32 tstamp_count, j;
 		struct ice_ts_desc *ts_desc;
 		struct timespec64 ts;
 		u32 tstamp;
 
+		smp_rmb();	/* order flag read before pointer read */
+		tstamp_ring = READ_ONCE(tx_ring->tstamp_ring);
+		if (unlikely(!tstamp_ring))
+			goto ring_kick;
+
+		tstamp_count = tstamp_ring->count;
+		j = tstamp_ring->next_to_use;
+
 		ts = ktime_to_timespec64(first->skb->tstamp);
 		tstamp = ts.tv_nsec >> ICE_TXTIME_CTX_RESOLUTION_128NS;
 
@@ -1555,6 +1563,7 @@ ice_tx_map(struct ice_tx_ring *tx_ring, struct ice_tx_buf *first,
 		tstamp_ring->next_to_use = j;
 		writel_relaxed(j, tstamp_ring->tail);
 	} else {
+ring_kick:
 		writel_relaxed(i, tx_ring->tail);
 	}
 	return;
@@ -1814,7 +1823,7 @@ ice_tx_prepare_vlan_flags(struct ice_tx_ring *tx_ring, struct ice_tx_buf *first)
 	 */
 	if (skb_vlan_tag_present(skb)) {
 		first->vid = skb_vlan_tag_get(skb);
-		if (tx_ring->flags & ICE_TX_FLAGS_RING_VLAN_L2TAG2)
+		if (test_bit(ICE_TX_RING_FLAGS_VLAN_L2TAG2, tx_ring->flags))
 			first->tx_flags |= ICE_TX_FLAGS_HW_OUTER_SINGLE_VLAN;
 		else
 			first->tx_flags |= ICE_TX_FLAGS_HW_VLAN;
diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.h b/drivers/net/ethernet/intel/ice/ice_txrx.h
index b6547e1b7c42..5e517f219379 100644
--- a/drivers/net/ethernet/intel/ice/ice_txrx.h
+++ b/drivers/net/ethernet/intel/ice/ice_txrx.h
@@ -212,6 +212,14 @@ enum ice_rx_dtype {
 	ICE_RX_DTYPE_SPLIT_ALWAYS	= 2,
 };
 
+enum ice_tx_ring_flags {
+	ICE_TX_RING_FLAGS_XDP,
+	ICE_TX_RING_FLAGS_VLAN_L2TAG1,
+	ICE_TX_RING_FLAGS_VLAN_L2TAG2,
+	ICE_TX_RING_FLAGS_TXTIME,
+	ICE_TX_RING_FLAGS_NBITS,
+};
+
 struct ice_pkt_ctx {
 	u64 cached_phctime;
 	__be16 vlan_proto;
@@ -352,11 +360,7 @@ struct ice_tx_ring {
 	u16 count;			/* Number of descriptors */
 	u16 q_index;			/* Queue number of ring */
 
-	u8 flags;
-#define ICE_TX_FLAGS_RING_XDP		BIT(0)
-#define ICE_TX_FLAGS_RING_VLAN_L2TAG1	BIT(1)
-#define ICE_TX_FLAGS_RING_VLAN_L2TAG2	BIT(2)
-#define ICE_TX_FLAGS_TXTIME		BIT(3)
+	DECLARE_BITMAP(flags, ICE_TX_RING_FLAGS_NBITS);
 
 	struct xsk_buff_pool *xsk_pool;
 
@@ -398,7 +402,7 @@ static inline bool ice_ring_ch_enabled(struct ice_tx_ring *ring)
 
 static inline bool ice_ring_is_xdp(struct ice_tx_ring *ring)
 {
-	return !!(ring->flags & ICE_TX_FLAGS_RING_XDP);
+	return test_bit(ICE_TX_RING_FLAGS_XDP, ring->flags);
 }
 
 enum ice_container_type {