[PATCH v2] net: mac80211: Add NULL checks for sta->sdata

[PATCH v2] net: mac80211: Add NULL checks for sta->sdata

[Jia-Ju Bai]

In a previous commit 69403bad97aa ("wifi: mac80211: sdata can be NULL
during AMPDU start"), sta->sdata can be NULL, and thus it should be 
checked before being used.

However, in the same call stack, sta->sdata is also used in the
following functions:

ieee80211_ba_session_work()
  ___ieee80211_stop_rx_ba_session(sta)
    ht_dbg(sta->sdata, ...); -> No check
    sdata_info(sta->sdata, ...); -> No check
    ieee80211_send_delba(sta->sdata, ...) -> No check
  ___ieee80211_start_rx_ba_session(sta)
    ht_dbg(sta->sdata, ...); -> No check
    ht_dbg_ratelimited(sta->sdata, ...); -> No check
  ieee80211_tx_ba_session_handle_start(sta)
    sdata = sta->sdata; if (!sdata) -> Add check by previous commit
  ___ieee80211_stop_tx_ba_session(sdata)
    ht_dbg(sta->sdata, ...); -> No check
  ieee80211_start_tx_ba_cb(sdata)
    sdata = sta->sdata; local = sdata->local -> No check
  ieee80211_stop_tx_ba_cb(sdata)
    ht_dbg(sta->sdata, ...); -> No check

Thus, to avoid possible null-pointer dereferences, the related checks
should be added.

These bugs are reported by a static analysis tool implemented by myself, 
and they are found by extending a known bug fixed in the previous commit. 
Thus, they could be theoretical bugs.

Signed-off-by: Jia-Ju Bai <baijiaju@buaa.edu.cn>
---
v2:
* Fix an error reported by checkpatch.pl, and make the bug finding
  process more clear in the description. Thanks for Simon's advice.
---
 net/mac80211/agg-rx.c | 68 ++++++++++++++++++++++++++-----------------
 net/mac80211/agg-tx.c | 16 ++++++++--
 2 files changed, 55 insertions(+), 29 deletions(-)

diff --git a/net/mac80211/agg-rx.c b/net/mac80211/agg-rx.c
index c6fa53230450..6616970785a2 100644
--- a/net/mac80211/agg-rx.c
+++ b/net/mac80211/agg-rx.c
@@ -80,19 +80,21 @@ void ___ieee80211_stop_rx_ba_session(struct sta_info *sta, u16 tid,
 	RCU_INIT_POINTER(sta->ampdu_mlme.tid_rx[tid], NULL);
 	__clear_bit(tid, sta->ampdu_mlme.agg_session_valid);
 
-	ht_dbg(sta->sdata,
-	       "Rx BA session stop requested for %pM tid %u %s reason: %d\n",
-	       sta->sta.addr, tid,
-	       initiator == WLAN_BACK_RECIPIENT ? "recipient" : "initiator",
-	       (int)reason);
+	if (sta->sdata) {
+		ht_dbg(sta->sdata,
+		       "Rx BA session stop requested for %pM tid %u %s reason: %d\n",
+		       sta->sta.addr, tid,
+		       initiator == WLAN_BACK_RECIPIENT ? "recipient" : "initiator",
+		       (int)reason);
+	}
 
-	if (drv_ampdu_action(local, sta->sdata, &params))
+	if (sta->sdata && drv_ampdu_action(local, sta->sdata, &params))
 		sdata_info(sta->sdata,
 			   "HW problem - can not stop rx aggregation for %pM tid %d\n",
 			   sta->sta.addr, tid);
 
 	/* check if this is a self generated aggregation halt */
-	if (initiator == WLAN_BACK_RECIPIENT && tx)
+	if (initiator == WLAN_BACK_RECIPIENT && tx && sta->sdata)
 		ieee80211_send_delba(sta->sdata, sta->sta.addr,
 				     tid, WLAN_BACK_RECIPIENT, reason);
 
@@ -279,17 +281,21 @@ void ___ieee80211_start_rx_ba_session(struct sta_info *sta,
 
 	if (!sta->sta.deflink.ht_cap.ht_supported &&
 	    !sta->sta.deflink.he_cap.has_he) {
-		ht_dbg(sta->sdata,
-		       "STA %pM erroneously requests BA session on tid %d w/o HT\n",
-		       sta->sta.addr, tid);
+		if (sta->sdata) {
+			ht_dbg(sta->sdata,
+			       "STA %pM erroneously requests BA session on tid %d w/o HT\n",
+			       sta->sta.addr, tid);
+		}
 		/* send a response anyway, it's an error case if we get here */
 		goto end;
 	}
 
 	if (test_sta_flag(sta, WLAN_STA_BLOCK_BA)) {
-		ht_dbg(sta->sdata,
-		       "Suspend in progress - Denying ADDBA request (%pM tid %d)\n",
-		       sta->sta.addr, tid);
+		if (sta->sdata) {
+			ht_dbg(sta->sdata,
+			       "Suspend in progress - Denying ADDBA request (%pM tid %d)\n",
+			       sta->sta.addr, tid);
+		}
 		goto end;
 	}
 
@@ -322,8 +328,10 @@ void ___ieee80211_start_rx_ba_session(struct sta_info *sta,
 		buf_size = sta->sta.max_rx_aggregation_subframes;
 	params.buf_size = buf_size;
 
-	ht_dbg(sta->sdata, "AddBA Req buf_size=%d for %pM\n",
-	       buf_size, sta->sta.addr);
+	if (sta->sdata) {
+		ht_dbg(sta->sdata, "AddBA Req buf_size=%d for %pM\n",
+		       buf_size, sta->sta.addr);
+	}
 
 	/* examine state machine */
 	lockdep_assert_held(&sta->ampdu_mlme.mtx);
@@ -332,9 +340,11 @@ void ___ieee80211_start_rx_ba_session(struct sta_info *sta,
 		if (sta->ampdu_mlme.tid_rx_token[tid] == dialog_token) {
 			struct tid_ampdu_rx *tid_rx;
 
-			ht_dbg_ratelimited(sta->sdata,
-					   "updated AddBA Req from %pM on tid %u\n",
-					   sta->sta.addr, tid);
+			if (sta->sdata) {
+				ht_dbg_ratelimited(sta->sdata,
+						   "updated AddBA Req from %pM on tid %u\n",
+						   sta->sta.addr, tid);
+			}
 			/* We have no API to update the timeout value in the
 			 * driver so reject the timeout update if the timeout
 			 * changed. If it did not change, i.e., no real update,
@@ -350,9 +360,11 @@ void ___ieee80211_start_rx_ba_session(struct sta_info *sta,
 			goto end;
 		}
 
-		ht_dbg_ratelimited(sta->sdata,
-				   "unexpected AddBA Req from %pM on tid %u\n",
-				   sta->sta.addr, tid);
+		if (sta->sdata) {
+			ht_dbg_ratelimited(sta->sdata,
+					   "unexpected AddBA Req from %pM on tid %u\n",
+					   sta->sta.addr, tid);
+		}
 
 		/* delete existing Rx BA session on the same tid */
 		___ieee80211_stop_rx_ba_session(sta, tid, WLAN_BACK_RECIPIENT,
@@ -362,9 +374,11 @@ void ___ieee80211_start_rx_ba_session(struct sta_info *sta,
 
 	if (ieee80211_hw_check(&local->hw, SUPPORTS_REORDERING_BUFFER)) {
 		ret = drv_ampdu_action(local, sta->sdata, &params);
-		ht_dbg(sta->sdata,
-		       "Rx A-MPDU request on %pM tid %d result %d\n",
-		       sta->sta.addr, tid, ret);
+		if (sta->sdata) {
+			ht_dbg(sta->sdata,
+			       "Rx A-MPDU request on %pM tid %d result %d\n",
+			       sta->sta.addr, tid, ret);
+		}
 		if (!ret)
 			status = WLAN_STATUS_SUCCESS;
 		goto end;
@@ -401,8 +415,10 @@ void ___ieee80211_start_rx_ba_session(struct sta_info *sta,
 		__skb_queue_head_init(&tid_agg_rx->reorder_buf[i]);
 
 	ret = drv_ampdu_action(local, sta->sdata, &params);
-	ht_dbg(sta->sdata, "Rx A-MPDU request on %pM tid %d result %d\n",
-	       sta->sta.addr, tid, ret);
+	if (sta->sdata) {
+		ht_dbg(sta->sdata, "Rx A-MPDU request on %pM tid %d result %d\n",
+		       sta->sta.addr, tid, ret);
+	}
 	if (ret) {
 		kfree(tid_agg_rx->reorder_buf);
 		kfree(tid_agg_rx->reorder_time);
diff --git a/net/mac80211/agg-tx.c b/net/mac80211/agg-tx.c
index f9514bacbd4a..03b31b6e7ac7 100644
--- a/net/mac80211/agg-tx.c
+++ b/net/mac80211/agg-tx.c
@@ -368,8 +368,10 @@ int ___ieee80211_stop_tx_ba_session(struct sta_info *sta, u16 tid,
 
 	spin_unlock_bh(&sta->lock);
 
-	ht_dbg(sta->sdata, "Tx BA session stop requested for %pM tid %u\n",
-	       sta->sta.addr, tid);
+	if (sta->sdata) {
+		ht_dbg(sta->sdata, "Tx BA session stop requested for %pM tid %u\n",
+		       sta->sta.addr, tid);
+	}
 
 	del_timer_sync(&tid_tx->addba_resp_timer);
 	del_timer_sync(&tid_tx->session_timer);
@@ -776,7 +778,12 @@ void ieee80211_start_tx_ba_cb(struct sta_info *sta, int tid,
 			      struct tid_ampdu_tx *tid_tx)
 {
 	struct ieee80211_sub_if_data *sdata = sta->sdata;
-	struct ieee80211_local *local = sdata->local;
+	struct ieee80211_local *local;
+
+	if (!sdata)
+		return;
+
+	local = sdata->local;
 
 	if (WARN_ON(test_and_set_bit(HT_AGG_STATE_DRV_READY, &tid_tx->state)))
 		return;
@@ -902,6 +909,9 @@ void ieee80211_stop_tx_ba_cb(struct sta_info *sta, int tid,
 	bool send_delba = false;
 	bool start_txq = false;
 
+	if (!sdata)
+		return;
+
 	ht_dbg(sdata, "Stopping Tx BA session for %pM tid %d\n",
 	       sta->sta.addr, tid);
 
-- 
2.34.1

Re: [PATCH v2] net: mac80211: Add NULL checks for sta->sdata

[Simon Horman]

On Tue, Mar 21, 2023 at 05:31:22PM +0800, Jia-Ju Bai wrote:
> In a previous commit 69403bad97aa ("wifi: mac80211: sdata can be NULL
> during AMPDU start"), sta->sdata can be NULL, and thus it should be 
> checked before being used.
> 
> However, in the same call stack, sta->sdata is also used in the
> following functions:
> 
> ieee80211_ba_session_work()
>   ___ieee80211_stop_rx_ba_session(sta)
>     ht_dbg(sta->sdata, ...); -> No check
>     sdata_info(sta->sdata, ...); -> No check
>     ieee80211_send_delba(sta->sdata, ...) -> No check
>   ___ieee80211_start_rx_ba_session(sta)
>     ht_dbg(sta->sdata, ...); -> No check
>     ht_dbg_ratelimited(sta->sdata, ...); -> No check
>   ieee80211_tx_ba_session_handle_start(sta)
>     sdata = sta->sdata; if (!sdata) -> Add check by previous commit
>   ___ieee80211_stop_tx_ba_session(sdata)
>     ht_dbg(sta->sdata, ...); -> No check
>   ieee80211_start_tx_ba_cb(sdata)
>     sdata = sta->sdata; local = sdata->local -> No check
>   ieee80211_stop_tx_ba_cb(sdata)
>     ht_dbg(sta->sdata, ...); -> No check
> 
> Thus, to avoid possible null-pointer dereferences, the related checks
> should be added.
> 
> These bugs are reported by a static analysis tool implemented by myself, 
> and they are found by extending a known bug fixed in the previous commit. 
> Thus, they could be theoretical bugs.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju@buaa.edu.cn>
> ---
> v2:
> * Fix an error reported by checkpatch.pl, and make the bug finding
>   process more clear in the description. Thanks for Simon's advice.
> ---
>  net/mac80211/agg-rx.c | 68 ++++++++++++++++++++++++++-----------------
>  net/mac80211/agg-tx.c | 16 ++++++++--
>  2 files changed, 55 insertions(+), 29 deletions(-)
> 
> diff --git a/net/mac80211/agg-rx.c b/net/mac80211/agg-rx.c
> index c6fa53230450..6616970785a2 100644
> --- a/net/mac80211/agg-rx.c
> +++ b/net/mac80211/agg-rx.c
> @@ -80,19 +80,21 @@ void ___ieee80211_stop_rx_ba_session(struct sta_info *sta, u16 tid,
>  	RCU_INIT_POINTER(sta->ampdu_mlme.tid_rx[tid], NULL);
>  	__clear_bit(tid, sta->ampdu_mlme.agg_session_valid);
>  
> -	ht_dbg(sta->sdata,
> -	       "Rx BA session stop requested for %pM tid %u %s reason: %d\n", > -	       sta->sta.addr, tid,
> -	       initiator == WLAN_BACK_RECIPIENT ? "recipient" : "initiator",
> -	       (int)reason);
> +	if (sta->sdata) {
> +		ht_dbg(sta->sdata,
> +		       "Rx BA session stop requested for %pM tid %u %s reason: %d\n",
> +		       sta->sta.addr, tid,
> +		       initiator == WLAN_BACK_RECIPIENT ? "recipient" : "initiator",
> +		       (int)reason);
> +	}

The first line of the body of ___ieee80211_stop_rx_ba_session() is:

	struct ieee80211_local *local = sta->sdata->local;

So a NULL pointer dereference will have occurred before
the checks this change adds to that function.


>  
> -	if (drv_ampdu_action(local, sta->sdata, &params))
> +	if (sta->sdata && drv_ampdu_action(local, sta->sdata, &params))
>  		sdata_info(sta->sdata,
>  			   "HW problem - can not stop rx aggregation for %pM tid %d\n",
>  			   sta->sta.addr, tid);
>  

...

> diff --git a/net/mac80211/agg-tx.c b/net/mac80211/agg-tx.c
> index f9514bacbd4a..03b31b6e7ac7 100644
> --- a/net/mac80211/agg-tx.c
> +++ b/net/mac80211/agg-tx.c
> @@ -368,8 +368,10 @@ int ___ieee80211_stop_tx_ba_session(struct sta_info *sta, u16 tid,
>  
>  	spin_unlock_bh(&sta->lock);
>  
> -	ht_dbg(sta->sdata, "Tx BA session stop requested for %pM tid %u\n",
> -	       sta->sta.addr, tid);
> +	if (sta->sdata) {
> +		ht_dbg(sta->sdata, "Tx BA session stop requested for %pM tid %u\n",
> +		       sta->sta.addr, tid);
> +	}

This seems clean :)

>  	del_timer_sync(&tid_tx->addba_resp_timer);
>  	del_timer_sync(&tid_tx->session_timer);
> @@ -776,7 +778,12 @@ void ieee80211_start_tx_ba_cb(struct sta_info *sta, int tid,
>  			      struct tid_ampdu_tx *tid_tx)
>  {
>  	struct ieee80211_sub_if_data *sdata = sta->sdata;
> -	struct ieee80211_local *local = sdata->local;
> +	struct ieee80211_local *local;
> +
> +	if (!sdata)
> +		return;

I'm not sure that silently ignoring non-existent sdata is the right approach.
Perhaps a WARN_ON or WARN_ONCE is appropriate?

> +
> +	local = sdata->local;
>  
>  	if (WARN_ON(test_and_set_bit(HT_AGG_STATE_DRV_READY, &tid_tx->state)))
>  		return;
> @@ -902,6 +909,9 @@ void ieee80211_stop_tx_ba_cb(struct sta_info *sta, int tid,
>  	bool send_delba = false;
>  	bool start_txq = false;
>  
> +	if (!sdata)
> +		return;
> +

Ditto.

>  	ht_dbg(sdata, "Stopping Tx BA session for %pM tid %d\n",
>  	       sta->sta.addr, tid);
>  

Re: [PATCH v2] net: mac80211: Add NULL checks for sta->sdata

[Jia-Ju Bai]

Hi Simon,

Thanks for your reply, and sorry for the delay.

On 2023/3/26 23:05, Simon Horman wrote:
> On Tue, Mar 21, 2023 at 05:31:22PM +0800, Jia-Ju Bai wrote:
>> In a previous commit 69403bad97aa ("wifi: mac80211: sdata can be NULL
>> during AMPDU start"), sta->sdata can be NULL, and thus it should be
>> checked before being used.
>>
>> However, in the same call stack, sta->sdata is also used in the
>> following functions:
>>
>> ieee80211_ba_session_work()
>>    ___ieee80211_stop_rx_ba_session(sta)
>>      ht_dbg(sta->sdata, ...); -> No check
>>      sdata_info(sta->sdata, ...); -> No check
>>      ieee80211_send_delba(sta->sdata, ...) -> No check
>>    ___ieee80211_start_rx_ba_session(sta)
>>      ht_dbg(sta->sdata, ...); -> No check
>>      ht_dbg_ratelimited(sta->sdata, ...); -> No check
>>    ieee80211_tx_ba_session_handle_start(sta)
>>      sdata = sta->sdata; if (!sdata) -> Add check by previous commit
>>    ___ieee80211_stop_tx_ba_session(sdata)
>>      ht_dbg(sta->sdata, ...); -> No check
>>    ieee80211_start_tx_ba_cb(sdata)
>>      sdata = sta->sdata; local = sdata->local -> No check
>>    ieee80211_stop_tx_ba_cb(sdata)
>>      ht_dbg(sta->sdata, ...); -> No check
>>
>> Thus, to avoid possible null-pointer dereferences, the related checks
>> should be added.
>>
>> These bugs are reported by a static analysis tool implemented by myself,
>> and they are found by extending a known bug fixed in the previous commit.
>> Thus, they could be theoretical bugs.
>>
>> Signed-off-by: Jia-Ju Bai <baijiaju@buaa.edu.cn>
>> ---
>> v2:
>> * Fix an error reported by checkpatch.pl, and make the bug finding
>>    process more clear in the description. Thanks for Simon's advice.
>> ---
>>   net/mac80211/agg-rx.c | 68 ++++++++++++++++++++++++++-----------------
>>   net/mac80211/agg-tx.c | 16 ++++++++--
>>   2 files changed, 55 insertions(+), 29 deletions(-)
>>
>> diff --git a/net/mac80211/agg-rx.c b/net/mac80211/agg-rx.c
>> index c6fa53230450..6616970785a2 100644
>> --- a/net/mac80211/agg-rx.c
>> +++ b/net/mac80211/agg-rx.c
>> @@ -80,19 +80,21 @@ void ___ieee80211_stop_rx_ba_session(struct sta_info *sta, u16 tid,
>>   	RCU_INIT_POINTER(sta->ampdu_mlme.tid_rx[tid], NULL);
>>   	__clear_bit(tid, sta->ampdu_mlme.agg_session_valid);
>>   
>> -	ht_dbg(sta->sdata,
>> -	       "Rx BA session stop requested for %pM tid %u %s reason: %d\n", > -	       sta->sta.addr, tid,
>> -	       initiator == WLAN_BACK_RECIPIENT ? "recipient" : "initiator",
>> -	       (int)reason);
>> +	if (sta->sdata) {
>> +		ht_dbg(sta->sdata,
>> +		       "Rx BA session stop requested for %pM tid %u %s reason: %d\n",
>> +		       sta->sta.addr, tid,
>> +		       initiator == WLAN_BACK_RECIPIENT ? "recipient" : "initiator",
>> +		       (int)reason);
>> +	}
> The first line of the body of ___ieee80211_stop_rx_ba_session() is:
>
> 	struct ieee80211_local *local = sta->sdata->local;
>
> So a NULL pointer dereference will have occurred before
> the checks this change adds to that function.

I checked the source code again (including the latest version 6.3-rc5).
The first line of the body of ___ieee80211_stop_rx_ba_session() is:

     struct ieee80211_local *local = sta->local;

Thus, there is no dereference of sta->sdata.

In a different function, namely ___ieee80211_start_rx_ba_session(), the 
first line is:

     struct ieee80211_local *local = sta->sdata->local;

Thus, there should be a NULL check for sta->sdata in this function.
I will add this in my patch v3.

>
>
>>   
>> -	if (drv_ampdu_action(local, sta->sdata, &params))
>> +	if (sta->sdata && drv_ampdu_action(local, sta->sdata, &params))
>>   		sdata_info(sta->sdata,
>>   			   "HW problem - can not stop rx aggregation for %pM tid %d\n",
>>   			   sta->sta.addr, tid);
>>   
> ...
>
>> diff --git a/net/mac80211/agg-tx.c b/net/mac80211/agg-tx.c
>> index f9514bacbd4a..03b31b6e7ac7 100644
>> --- a/net/mac80211/agg-tx.c
>> +++ b/net/mac80211/agg-tx.c
>> @@ -368,8 +368,10 @@ int ___ieee80211_stop_tx_ba_session(struct sta_info *sta, u16 tid,
>>   
>>   	spin_unlock_bh(&sta->lock);
>>   
>> -	ht_dbg(sta->sdata, "Tx BA session stop requested for %pM tid %u\n",
>> -	       sta->sta.addr, tid);
>> +	if (sta->sdata) {
>> +		ht_dbg(sta->sdata, "Tx BA session stop requested for %pM tid %u\n",
>> +		       sta->sta.addr, tid);
>> +	}
> This seems clean :)
>
>>   	del_timer_sync(&tid_tx->addba_resp_timer);
>>   	del_timer_sync(&tid_tx->session_timer);
>> @@ -776,7 +778,12 @@ void ieee80211_start_tx_ba_cb(struct sta_info *sta, int tid,
>>   			      struct tid_ampdu_tx *tid_tx)
>>   {
>>   	struct ieee80211_sub_if_data *sdata = sta->sdata;
>> -	struct ieee80211_local *local = sdata->local;
>> +	struct ieee80211_local *local;
>> +
>> +	if (!sdata)
>> +		return;
> I'm not sure that silently ignoring non-existent sdata is the right approach.
> Perhaps a WARN_ON or WARN_ONCE is appropriate?

Okay, I will use WARN_ON  in my patch v3.

>
>> +
>> +	local = sdata->local;
>>   
>>   	if (WARN_ON(test_and_set_bit(HT_AGG_STATE_DRV_READY, &tid_tx->state)))
>>   		return;
>> @@ -902,6 +909,9 @@ void ieee80211_stop_tx_ba_cb(struct sta_info *sta, int tid,
>>   	bool send_delba = false;
>>   	bool start_txq = false;
>>   
>> +	if (!sdata)
>> +		return;
>> +
> Ditto.

Okay, I will use WARN_ON  in my patch v3.

>
>>   	ht_dbg(sdata, "Stopping Tx BA session for %pM tid %d\n",
>>   	       sta->sta.addr, tid);
>>   


Best wishes,
Jia-Ju Bai

Re: [PATCH v2] net: mac80211: Add NULL checks for sta->sdata

[Simon Horman]

On Tue, Apr 04, 2023 at 05:58:13PM +0800, Jia-Ju Bai wrote:
> Hi Simon,
> 
> Thanks for your reply, and sorry for the delay.
> 
> On 2023/3/26 23:05, Simon Horman wrote:
> > On Tue, Mar 21, 2023 at 05:31:22PM +0800, Jia-Ju Bai wrote:
> > > In a previous commit 69403bad97aa ("wifi: mac80211: sdata can be NULL
> > > during AMPDU start"), sta->sdata can be NULL, and thus it should be
> > > checked before being used.
> > > 
> > > However, in the same call stack, sta->sdata is also used in the
> > > following functions:
> > > 
> > > ieee80211_ba_session_work()
> > >    ___ieee80211_stop_rx_ba_session(sta)
> > >      ht_dbg(sta->sdata, ...); -> No check
> > >      sdata_info(sta->sdata, ...); -> No check
> > >      ieee80211_send_delba(sta->sdata, ...) -> No check
> > >    ___ieee80211_start_rx_ba_session(sta)
> > >      ht_dbg(sta->sdata, ...); -> No check
> > >      ht_dbg_ratelimited(sta->sdata, ...); -> No check
> > >    ieee80211_tx_ba_session_handle_start(sta)
> > >      sdata = sta->sdata; if (!sdata) -> Add check by previous commit
> > >    ___ieee80211_stop_tx_ba_session(sdata)
> > >      ht_dbg(sta->sdata, ...); -> No check
> > >    ieee80211_start_tx_ba_cb(sdata)
> > >      sdata = sta->sdata; local = sdata->local -> No check
> > >    ieee80211_stop_tx_ba_cb(sdata)
> > >      ht_dbg(sta->sdata, ...); -> No check
> > > 
> > > Thus, to avoid possible null-pointer dereferences, the related checks
> > > should be added.
> > > 
> > > These bugs are reported by a static analysis tool implemented by myself,
> > > and they are found by extending a known bug fixed in the previous commit.
> > > Thus, they could be theoretical bugs.
> > > 
> > > Signed-off-by: Jia-Ju Bai <baijiaju@buaa.edu.cn>
> > > ---
> > > v2:
> > > * Fix an error reported by checkpatch.pl, and make the bug finding
> > >    process more clear in the description. Thanks for Simon's advice.
> > > ---
> > >   net/mac80211/agg-rx.c | 68 ++++++++++++++++++++++++++-----------------
> > >   net/mac80211/agg-tx.c | 16 ++++++++--
> > >   2 files changed, 55 insertions(+), 29 deletions(-)
> > > 
> > > diff --git a/net/mac80211/agg-rx.c b/net/mac80211/agg-rx.c
> > > index c6fa53230450..6616970785a2 100644
> > > --- a/net/mac80211/agg-rx.c
> > > +++ b/net/mac80211/agg-rx.c
> > > @@ -80,19 +80,21 @@ void ___ieee80211_stop_rx_ba_session(struct sta_info *sta, u16 tid,
> > >   	RCU_INIT_POINTER(sta->ampdu_mlme.tid_rx[tid], NULL);
> > >   	__clear_bit(tid, sta->ampdu_mlme.agg_session_valid);
> > > -	ht_dbg(sta->sdata,
> > > -	       "Rx BA session stop requested for %pM tid %u %s reason: %d\n", > -	       sta->sta.addr, tid,
> > > -	       initiator == WLAN_BACK_RECIPIENT ? "recipient" : "initiator",
> > > -	       (int)reason);
> > > +	if (sta->sdata) {
> > > +		ht_dbg(sta->sdata,
> > > +		       "Rx BA session stop requested for %pM tid %u %s reason: %d\n",
> > > +		       sta->sta.addr, tid,
> > > +		       initiator == WLAN_BACK_RECIPIENT ? "recipient" : "initiator",
> > > +		       (int)reason);
> > > +	}
> > The first line of the body of ___ieee80211_stop_rx_ba_session() is:
> > 
> > 	struct ieee80211_local *local = sta->sdata->local;
> > 
> > So a NULL pointer dereference will have occurred before
> > the checks this change adds to that function.
> 
> I checked the source code again (including the latest version 6.3-rc5).
> The first line of the body of ___ieee80211_stop_rx_ba_session() is:
> 
>     struct ieee80211_local *local = sta->local;
> 
> Thus, there is no dereference of sta->sdata.

My mistake, sorry about that.

> In a different function, namely ___ieee80211_start_rx_ba_session(), the
> first line is:
> 
>     struct ieee80211_local *local = sta->sdata->local;

Yes, I see that too.

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