[PATCH 5.15.y] wifi: iwlwifi: read txq->read_ptr under lock

[PATCH 5.15.y] wifi: iwlwifi: read txq->read_ptr under lock

[Robert Garcia]

From: Johannes Berg <johannes.berg@intel.com>

[ Upstream commit c2ace6300600c634553657785dfe5ea0ed688ac2 ]

If we read txq->read_ptr without lock, we can read the same
value twice, then obtain the lock, and reclaim from there
to two different places, but crucially reclaim the same
entry twice, resulting in the WARN_ONCE() a little later.
Fix that by reading txq->read_ptr under lock.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20240319100755.bf4c62196504.I978a7ca56c6bd6f1bf42c15aa923ba03366a840b@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
[ Change read_ptr definition according to commit
413be839bfca9("wifi: iwlwifi: add a validity check of queue_id in iwl_txq_reclaim"). ]
Signed-off-by: Robert Garcia <rob_garcia@163.com>
---
 drivers/net/wireless/intel/iwlwifi/queue/tx.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/intel/iwlwifi/queue/tx.c b/drivers/net/wireless/intel/iwlwifi/queue/tx.c
index cd852b95d812..d8322a40409b 100644
--- a/drivers/net/wireless/intel/iwlwifi/queue/tx.c
+++ b/drivers/net/wireless/intel/iwlwifi/queue/tx.c
@@ -1524,7 +1524,7 @@ void iwl_txq_reclaim(struct iwl_trans *trans, int txq_id, int ssn,
 {
 	struct iwl_txq *txq = trans->txqs.txq[txq_id];
 	int tfd_num = iwl_txq_get_cmd_index(txq, ssn);
-	int read_ptr = iwl_txq_get_cmd_index(txq, txq->read_ptr);
+	int read_ptr;
 	int last_to_free;
 
 	/* This function is not meant to release cmd queue*/
@@ -1532,6 +1532,7 @@ void iwl_txq_reclaim(struct iwl_trans *trans, int txq_id, int ssn,
 		return;
 
 	spin_lock_bh(&txq->lock);
+	read_ptr = iwl_txq_get_cmd_index(txq, txq->read_ptr);
 
 	if (!test_bit(txq_id, trans->txqs.queue_used)) {
 		IWL_DEBUG_TX_QUEUES(trans, "Q %d inactive - ignoring idx %d\n",
-- 
2.34.1