[PATCH 4/5] wifi: ath12k: avoid IDR mutation during pending mgmt TX cleanup

[jiale yao]

At 2026-09-28 13:49:54, "Rameshkumar Sundaram" <rameshkumar.sundaram at oss.qualcomm.com> wrote:
>On 9/26/2026 9:18 PM, Jiale Yao wrote:
>> ath12k_mac_tx_mgmt_pending_free() is passed as an idr_for_each()
>> callback and removes the current entry from txmgmt_idr. This can
>> invalidate the radix-tree iterator retained by idr_for_each().
>> 
>> Both callers destroy the IDR immediately after the walk, so removing
>> each entry in the callback is unnecessary. Split skb release from IDR
>> removal and let the callback release the supplied skb without updating
>> the IDR. The following idr_destroy() tears down the IDR itself.
>> 
>> Fixes: d889913205cf ("wifi: ath12k: driver for Qualcomm Wi-Fi 7 devices")
>> Signed-off-by: Jiale Yao <yaojiale02 at 163.com>
>> ---
>>   drivers/net/wireless/ath/ath12k/mac.c | 25 +++++++++++++++----------
>>   1 file changed, 15 insertions(+), 10 deletions(-)
>> 
>> diff --git a/drivers/net/wireless/ath/ath12k/mac.c b/drivers/net/wireless/ath/ath12k/mac.c
>> index 99bf5cf79d10..7695b21149d1 100644
>> --- a/drivers/net/wireless/ath/ath12k/mac.c
>> +++ b/drivers/net/wireless/ath/ath12k/mac.c
>> @@ -9166,18 +9166,11 @@ static void ath12k_mgmt_over_wmi_tx_drop(struct ath12k *ar, struct sk_buff *skb)
>>   		wake_up(&ar->txmgmt_empty_waitq);
>>   }
>>   
>> -static void ath12k_mac_tx_mgmt_free(struct ath12k *ar, int buf_id)
>> +static void ath12k_mac_tx_mgmt_free_skb(struct ath12k *ar,
>> +					struct sk_buff *msdu)
>>   {
>> -	struct sk_buff *msdu;
>>   	struct ieee80211_tx_info *info;
>>   
>> -	spin_lock_bh(&ar->txmgmt_idr_lock);
>> -	msdu = idr_remove(&ar->txmgmt_idr, buf_id);
>> -	spin_unlock_bh(&ar->txmgmt_idr_lock);
>> -
>> -	if (!msdu)
>> -		return;
>> -
>>   	dma_unmap_single(ar->ab->dev, ATH12K_SKB_CB(msdu)->paddr, msdu->len,
>>   			 DMA_TO_DEVICE);
>>   
>> @@ -9187,11 +9180,23 @@ static void ath12k_mac_tx_mgmt_free(struct ath12k *ar, int buf_id)
>>   	ath12k_mgmt_over_wmi_tx_drop(ar, msdu);
>>   }
>>   
>> +static void ath12k_mac_tx_mgmt_free(struct ath12k *ar, int buf_id)
>> +{
>> +	struct sk_buff *msdu;
>> +
>> +	spin_lock_bh(&ar->txmgmt_idr_lock);
>> +	msdu = idr_remove(&ar->txmgmt_idr, buf_id);
>> +	spin_unlock_bh(&ar->txmgmt_idr_lock);
>> +
>> +	if (msdu)
>> +		ath12k_mac_tx_mgmt_free_skb(ar, msdu);
>> +}
>> +
>>   int ath12k_mac_tx_mgmt_pending_free(int buf_id, void *skb, void *ctx)
>>   {
>>   	struct ath12k *ar = ctx;
>>   
>> -	ath12k_mac_tx_mgmt_free(ar, buf_id);
>> +	ath12k_mac_tx_mgmt_free_skb(ar, skb);
>
>this now keeps the freed skbs in the idr for the whole time 
>idr_for_each() runs as opposed to previous implementation which removed 
>the idr entry as well which looked safe.

Thanks for the review.

The original issue is the same as the one fixed by commit c38b1e19485a
("firmware: arm_scmi: Avoid IDR updates while cleaning channels").
ath12k_mac_tx_mgmt_pending_free() is called from idr_for_each(), and
ath12k_mac_tx_mgmt_free() removes the current entry from that same IDR
before the iterator advances. This can invalidate the iterator state.

You are right that my patch leaves freed skb pointers in the IDR until
idr_destroy(), which is undesirable.

I will send a v2 using idr_for_each_entry(), which performs a fresh
idr_get_next() lookup for each iteration. The entry will then be removed
from the IDR before its skb is freed, avoiding both the invalid iterator
state and stale skb pointers.

Thanks,
Jiale


>
>
>>   
>>   	return 0;
>>   }
>
>
>-- 
>Ramesh