[PATCH] ath11k: fix a locking bug in ath11k_mac_op_start()

[PATCH] ath11k: fix a locking bug in ath11k_mac_op_start()

[Dan Carpenter]

This error path leads to a Smatch warning:

    drivers/net/wireless/ath/ath11k/mac.c:4269 ath11k_mac_op_start()
    error: double unlocked '&ar->conf_mutex' (orig line 4251)

We're not holding the lock when we do the "goto err;" so it leads to a
double unlock.  We should hold the lock because the error path sets
"ar->state" so the right fix is to take the lock before doing the goto.

Fixes: c83c500b55b6 ("ath11k: enable idle power save mode")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
 drivers/net/wireless/ath/ath11k/mac.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/wireless/ath/ath11k/mac.c b/drivers/net/wireless/ath/ath11k/mac.c
index c1608f64ea95..12e981e9e3d7 100644
--- a/drivers/net/wireless/ath/ath11k/mac.c
+++ b/drivers/net/wireless/ath/ath11k/mac.c
@@ -4259,6 +4259,7 @@ static int ath11k_mac_op_start(struct ieee80211_hw *hw)
 						1, pdev->pdev_id);
 		if (ret) {
 			ath11k_err(ab, "failed to enable idle ps: %d\n", ret);
+			mutex_lock(&ar->conf_mutex);
 			goto err;
 		}
 	}
-- 
2.29.2

Re: [PATCH] ath11k: fix a locking bug in ath11k_mac_op_start()

[Peter Oh]

On 2/1/21 4:24 AM, Dan Carpenter wrote:
> This error path leads to a Smatch warning:
>
>      drivers/net/wireless/ath/ath11k/mac.c:4269 ath11k_mac_op_start()
>      error: double unlocked '&ar->conf_mutex' (orig line 4251)
>
> We're not holding the lock when we do the "goto err;" so it leads to a
> double unlock.  We should hold the lock because the error path sets
> "ar->state" so the right fix is to take the lock before doing the goto.
>
> Fixes: c83c500b55b6 ("ath11k: enable idle power save mode")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
>   drivers/net/wireless/ath/ath11k/mac.c | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/drivers/net/wireless/ath/ath11k/mac.c b/drivers/net/wireless/ath/ath11k/mac.c
> index c1608f64ea95..12e981e9e3d7 100644
> --- a/drivers/net/wireless/ath/ath11k/mac.c
> +++ b/drivers/net/wireless/ath/ath11k/mac.c
> @@ -4259,6 +4259,7 @@ static int ath11k_mac_op_start(struct ieee80211_hw *hw)
>   						1, pdev->pdev_id);
>   		if (ret) {
>   			ath11k_err(ab, "failed to enable idle ps: %d\n", ret);
> +			mutex_lock(&ar->conf_mutex);
>   			goto err;
>   		}
>   	}
It seems moving idle_ps condition in between ath11k_wmi_pdev_lro_cfg() 
and mutex_unlock()
  is a better way in this case.

Thanks,
Peter

Re: [PATCH] ath11k: fix a locking bug in ath11k_mac_op_start()

[Kalle Valo]

Peter Oh <peter.oh@eero.com> writes:

> On 2/1/21 4:24 AM, Dan Carpenter wrote:
>> This error path leads to a Smatch warning:
>>
>>      drivers/net/wireless/ath/ath11k/mac.c:4269 ath11k_mac_op_start()
>>      error: double unlocked '&ar->conf_mutex' (orig line 4251)
>>
>> We're not holding the lock when we do the "goto err;" so it leads to a
>> double unlock.  We should hold the lock because the error path sets
>> "ar->state" so the right fix is to take the lock before doing the goto.
>>
>> Fixes: c83c500b55b6 ("ath11k: enable idle power save mode")
>> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>> ---
>>   drivers/net/wireless/ath/ath11k/mac.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/net/wireless/ath/ath11k/mac.c b/drivers/net/wireless/ath/ath11k/mac.c
>> index c1608f64ea95..12e981e9e3d7 100644
>> --- a/drivers/net/wireless/ath/ath11k/mac.c
>> +++ b/drivers/net/wireless/ath/ath11k/mac.c
>> @@ -4259,6 +4259,7 @@ static int ath11k_mac_op_start(struct ieee80211_hw *hw)
>>   						1, pdev->pdev_id);
>>   		if (ret) {
>>   			ath11k_err(ab, "failed to enable idle ps: %d\n", ret);
>> +			mutex_lock(&ar->conf_mutex);
>>   			goto err;
>>   		}
>>   	}
>
> It seems moving idle_ps condition in between ath11k_wmi_pdev_lro_cfg()
> and mutex_unlock()
>  is a better way in this case.

I agree. In Dan's approach I'm worried about the race when we unlock and
lock again, the state can change in that case.

-- 
https://patchwork.kernel.org/project/linux-wireless/list/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches