linux-kernel - Re: [PATCH 1/2] wifi: ath11k: fix temperature event locking

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Message-ID: <4233c8af-5911-40bf-b5ba-dd0a63863a45@quicinc.com>
Date:   Thu, 19 Oct 2023 08:04:55 -0700
From:   Jeff Johnson <quic_jjohnson@...cinc.com>
To:     Johan Hovold <johan+linaro@...nel.org>,
        Kalle Valo <kvalo@...nel.org>
CC:     Pradeep Kumar Chitrapu <quic_pradeepc@...cinc.com>,
        <ath11k@...ts.infradead.org>, <linux-wireless@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>
Subject: Re: [PATCH 1/2] wifi: ath11k: fix temperature event locking

On 10/19/2023 3:42 AM, Johan Hovold wrote:
> The ath11k active pdevs are protected by RCU but the temperature event
> handling code calling ath11k_mac_get_ar_by_pdev_id() was not marked as a
> read-side critical section as reported by RCU lockdep:

How do I enable this? Just enable CONFIG_PROVE_RCU?
Of course I'd also need to exercise the code path...

> 
> 	=============================
> 	WARNING: suspicious RCU usage
> 	6.6.0-rc6 #7 Not tainted
> 	-----------------------------
> 	drivers/net/wireless/ath/ath11k/mac.c:638 suspicious rcu_dereference_check() usage!
> 
> 	other info that might help us debug this:
> 
> 	rcu_scheduler_active = 2, debug_locks = 1
> 	no locks held by swapper/0/0.
> 	...
> 	Call trace:
> 	...
> 	 lockdep_rcu_suspicious+0x16c/0x22c
> 	 ath11k_mac_get_ar_by_pdev_id+0x194/0x1b0 [ath11k]
> 	 ath11k_wmi_tlv_op_rx+0xa84/0x2c1c [ath11k]
> 	 ath11k_htc_rx_completion_handler+0x388/0x510 [ath11k]
> 
> Mark the code in question as an RCU read-side critical section to avoid
> any potential use-after-free issues.
> 
> Fixes: a41d10348b01 ("ath11k: add thermal sensor device support")
> Cc: stable@...r.kernel.org      # 5.7
> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> ---
>   drivers/net/wireless/ath/ath11k/wmi.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/net/wireless/ath/ath11k/wmi.c b/drivers/net/wireless/ath/ath11k/wmi.c
> index 23ad6825e5be..980ff588325d 100644
> --- a/drivers/net/wireless/ath/ath11k/wmi.c
> +++ b/drivers/net/wireless/ath/ath11k/wmi.c
> @@ -8383,6 +8383,8 @@ ath11k_wmi_pdev_temperature_event(struct ath11k_base *ab,
>   	ath11k_dbg(ab, ATH11K_DBG_WMI, "event pdev temperature ev temp %d pdev_id %d\n",
>   		   ev->temp, ev->pdev_id);
>   
> +	rcu_read_lock();
> +
>   	ar = ath11k_mac_get_ar_by_pdev_id(ab, ev->pdev_id);
>   	if (!ar) {
>   		ath11k_warn(ab, "invalid pdev id in pdev temperature ev %d", ev->pdev_id);

aren't you missing an unlock() in this error path?

perhaps have a goto cleanup that does both the unlock() and the kfree()?

> @@ -8392,6 +8394,8 @@ ath11k_wmi_pdev_temperature_event(struct ath11k_base *ab,
>   
>   	ath11k_thermal_event_temperature(ar, ev->temp);
>   
> +	rcu_read_unlock();
> +
>   	kfree(tb);
>   }
>