RE: [PATCH] rtw89: fix RCU usage in rtw89_core_txq_push()

[Pkshih <pkshih@realtek.com>]

> -----Original Message-----
> From: Jiri Kosina <jkosina@suse.cz>
> Sent: Wednesday, February 16, 2022 3:38 AM
> To: Kalle Valo <kvalo@kernel.org>
> Cc: Johannes Berg <johannes@sipsolutions.net>; linux-wireless@vger.kernel.org;
> linux-kernel@vger.kernel.org; Pkshih <pkshih@realtek.com>
> Subject: [PATCH] rtw89: fix RCU usage in rtw89_core_txq_push()
> 
> From: Jiri Kosina <jkosina@suse.cz>
> Subject: [PATCH] rtw89: fix RCU usage in rtw89_core_txq_push()
> 
> ieee80211_tx_h_select_key() is performing a series of RCU dereferences,
> but rtw89_core_txq_push() is calling it (via ieee80211_tx_dequeue_ni())
> without RCU read-side lock held; fix that.
> 
> This addresses the splat below.
> 
>  =============================
>  WARNING: suspicious RCU usage
>  5.17.0-rc4-00003-gccad664b7f14 #3 Tainted: G            E
>  -----------------------------
>  net/mac80211/tx.c:593 suspicious rcu_dereference_check() usage!
> 
>  other info that might help us debug this:
> 
>  rcu_scheduler_active = 2, debug_locks = 1
>  2 locks held by kworker/u33:0/184:
>   #0: ffff9c0b14811d38 ((wq_completion)rtw89_tx_wq){+.+.}-{0:0}, at: process_one_work+0x258/0x660
>   #1: ffffb97380cf3e78 ((work_completion)(&rtwdev->txq_work)){+.+.}-{0:0}, at:
> process_one_work+0x258/0x660
> 
>  stack backtrace:
>  CPU: 8 PID: 184 Comm: kworker/u33:0 Tainted: G            E     5.17.0-rc4-00003-gccad664b7f14 #3
> 473b49ab0e7c2d6af2900c756bfd04efd7a9de13
>  Hardware name: LENOVO 20UJS2B905/20UJS2B905, BIOS R1CET63W(1.32 ) 04/09/2021
>  Workqueue: rtw89_tx_wq rtw89_core_txq_work [rtw89_core]
>  Call Trace:
>   <TASK>
>   dump_stack_lvl+0x58/0x71
>   ieee80211_tx_h_select_key+0x2c0/0x530 [mac80211 911c23e2351c0ae60b597a67b1204a5ea955e365]
>   ieee80211_tx_dequeue+0x1a7/0x1260 [mac80211 911c23e2351c0ae60b597a67b1204a5ea955e365]
>   rtw89_core_txq_work+0x1a6/0x420 [rtw89_core b39ba493f2e517ad75e0f8187ecc24edf58bbbea]
>   process_one_work+0x2d8/0x660
>   worker_thread+0x39/0x3e0
>   ? process_one_work+0x660/0x660
>   kthread+0xe5/0x110
>   ? kthread_complete_and_exit+0x20/0x20
>   ret_from_fork+0x22/0x30
>   </TASK>
> 
>  =============================
>  WARNING: suspicious RCU usage
>  5.17.0-rc4-00003-gccad664b7f14 #3 Tainted: G            E
>  -----------------------------
>  net/mac80211/tx.c:607 suspicious rcu_dereference_check() usage!
> 
>  other info that might help us debug this:
> 
>  rcu_scheduler_active = 2, debug_locks = 1
>  2 locks held by kworker/u33:0/184:
>   #0: ffff9c0b14811d38 ((wq_completion)rtw89_tx_wq){+.+.}-{0:0}, at: process_one_work+0x258/0x660
>   #1: ffffb97380cf3e78 ((work_completion)(&rtwdev->txq_work)){+.+.}-{0:0}, at:
> process_one_work+0x258/0x660
> 
>  stack backtrace:
>  CPU: 8 PID: 184 Comm: kworker/u33:0 Tainted: G            E     5.17.0-rc4-00003-gccad664b7f14 #3
> 473b49ab0e7c2d6af2900c756bfd04efd7a9de13
>  Hardware name: LENOVO 20UJS2B905/20UJS2B905, BIOS R1CET63W(1.32 ) 04/09/2021
>  Workqueue: rtw89_tx_wq rtw89_core_txq_work [rtw89_core]
>  Call Trace:
>   <TASK>
>   dump_stack_lvl+0x58/0x71
>   ieee80211_tx_h_select_key+0x464/0x530 [mac80211 911c23e2351c0ae60b597a67b1204a5ea955e365]
>   ieee80211_tx_dequeue+0x1a7/0x1260 [mac80211 911c23e2351c0ae60b597a67b1204a5ea955e365]
>   rtw89_core_txq_work+0x1a6/0x420 [rtw89_core b39ba493f2e517ad75e0f8187ecc24edf58bbbea]
>   process_one_work+0x2d8/0x660
>   worker_thread+0x39/0x3e0
>   ? process_one_work+0x660/0x660
>   kthread+0xe5/0x110
>   ? kthread_complete_and_exit+0x20/0x20
>   ret_from_fork+0x22/0x30
>   </TASK>
> 
> Signed-off-by: Jiri Kosina <jkosina@suse.cz>

Acked-by: Ping-Ke Shih <pkshih@realtek.com>

Thanks for your finding.

> ---
>  drivers/net/wireless/realtek/rtw89/core.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/realtek/rtw89/core.c b/drivers/net/wireless/realtek/rtw89/core.c
> index a0737eea9f81..9632e7f218dd 100644
> --- a/drivers/net/wireless/realtek/rtw89/core.c
> +++ b/drivers/net/wireless/realtek/rtw89/core.c
> @@ -1509,11 +1509,12 @@ static void rtw89_core_txq_push(struct rtw89_dev *rtwdev,
>  	unsigned long i;
>  	int ret;
> 
> +	rcu_read_lock();
>  	for (i = 0; i < frame_cnt; i++) {
>  		skb = ieee80211_tx_dequeue_ni(rtwdev->hw, txq);
>  		if (!skb) {
>  			rtw89_debug(rtwdev, RTW89_DBG_TXRX, "dequeue a NULL skb\n");
> -			return;
> +			goto out;
>  		}
>  		rtw89_core_txq_check_agg(rtwdev, rtwtxq, skb);
>  		ret = rtw89_core_tx_write(rtwdev, vif, sta, skb, NULL);
> @@ -1523,6 +1524,8 @@ static void rtw89_core_txq_push(struct rtw89_dev *rtwdev,
>  			break;
>  		}
>  	}
> +out:
> +	rcu_read_unlock();
>  }
> 
>  static u32 rtw89_check_and_reclaim_tx_resource(struct rtw89_dev *rtwdev, u8 tid)
> 
> --
> Jiri Kosina
> SUSE Labs
> 
> 
> ------Please consider the environment before printing this e-mail.