[PATCH ath12k-ng] wifi: ath12k: add the missing RCU lock in ath12k_dp_tx_free_txbuf()

[Baochen Qiang]

RCU read lock is missing in ath12k_dp_tx_free_txbuf() before calling
ath12k_dp_to_pdev_dp(), causing below warning:

WARNING: suspicious RCU usage
-----------------------------
drivers/net/wireless/ath/ath12k/dp.h:653 ath12k dp to dp pdev called without rcu lock!
Call Trace:
 <IRQ>
 show_stack
 dump_stack_lvl
 dump_stack
 lockdep_rcu_suspicious.cold
 ath12k_dp_tx_free_txbuf
 ath12k_wifi7_dp_tx_completion_handler
 ath12k_wifi7_dp_service_srng
 ath12k_pci_ext_grp_napi_poll
 [...]
 </IRQ>

Invoke guard(rcu) to fix it.

Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.1.c5-00302-QCAHMTSWPL_V1.0_V2.0_SILICONZ-1.115823.3

Signed-off-by: Baochen Qiang <baochen.qiang at oss.qualcomm.com>
---
 drivers/net/wireless/ath/ath12k/dp_tx.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/ath12k/dp_tx.c b/drivers/net/wireless/ath/ath12k/dp_tx.c
index 1d4444f3936f..c10da6195c9c 100644
--- a/drivers/net/wireless/ath/ath12k/dp_tx.c
+++ b/drivers/net/wireless/ath/ath12k/dp_tx.c
@@ -194,8 +194,6 @@ void ath12k_dp_tx_free_txbuf(struct ath12k_dp *dp,
 
 	skb_cb = ATH12K_SKB_CB(msdu);
 
-	dp_pdev = ath12k_dp_to_pdev_dp(dp, pdev_idx);
-
 	dma_unmap_single(dp->dev, skb_cb->paddr, msdu->len, DMA_TO_DEVICE);
 	if (skb_cb->paddr_ext_desc) {
 		dma_unmap_single(dp->dev, skb_cb->paddr_ext_desc,
@@ -203,6 +201,10 @@ void ath12k_dp_tx_free_txbuf(struct ath12k_dp *dp,
 		dev_kfree_skb_any(desc_params->skb_ext_desc);
 	}
 
+	guard(rcu)();
+
+	dp_pdev = ath12k_dp_to_pdev_dp(dp, pdev_idx);
+
 	ieee80211_free_txskb(ath12k_pdev_dp_to_hw(dp_pdev), msdu);
 
 	if (atomic_dec_and_test(&dp_pdev->num_tx_pending))

---
base-commit: 7cd7392a07782b8ad4aa6360e4be1967af2eab04
change-id: 20251118-ath12k-fix-missing-rcu-lock-51484e258da9

Best regards,
-- 
Baochen Qiang <baochen.qiang at oss.qualcomm.com>