[RFC PATCH] staging: rtl8723bs: fix potential race in expire_timeout_chk

[RFC PATCH] staging: rtl8723bs: fix potential race in expire_timeout_chk

[Minu Jin]

The expire_timeout_chk function currently do lock and unlock inside the
loop before calling rtw_free_stainfo().

This can be risky as the list might be changed
when the lock is briefly released.

To fix this, move expired sta_info entries into a local free_list while
holding the lock, and then perform the actual freeing after the lock is
released.

Signed-off-by: Minu Jin <s9430939@naver.com>
---
Hi,

I noticed this lock-unlock pattern in expire_timeout_chk() while
studying the code and it looked like a potential race condition.

I've refactored the code to use a local list so we can handle the
cleanup after releasing the lock. What do you think about this approach?

Any feedback is appreciated.

 drivers/staging/rtl8723bs/core/rtw_ap.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/drivers/staging/rtl8723bs/core/rtw_ap.c b/drivers/staging/rtl8723bs/core/rtw_ap.c
index 67197c7d4a4d..5947f6363ab0 100644
--- a/drivers/staging/rtl8723bs/core/rtw_ap.c
+++ b/drivers/staging/rtl8723bs/core/rtw_ap.c
@@ -179,6 +179,9 @@ void expire_timeout_chk(struct adapter *padapter)
 	u8 chk_alive_num = 0;
 	char chk_alive_list[NUM_STA];
 	int i;
+	struct list_head free_list;
+
+	INIT_LIST_HEAD(&free_list);
 
 	spin_lock_bh(&pstapriv->auth_list_lock);
 
@@ -190,19 +193,21 @@ void expire_timeout_chk(struct adapter *padapter)
 		if (psta->expire_to > 0) {
 			psta->expire_to--;
 			if (psta->expire_to == 0) {
-				list_del_init(&psta->auth_list);
+				list_move(&psta->auth_list, &free_list);
 				pstapriv->auth_list_cnt--;
-
-				spin_unlock_bh(&pstapriv->auth_list_lock);
-
-				rtw_free_stainfo(padapter, psta);
-
-				spin_lock_bh(&pstapriv->auth_list_lock);
 			}
 		}
 	}
 
 	spin_unlock_bh(&pstapriv->auth_list_lock);
+
+	/* free free_list */
+	list_for_each_safe(plist, tmp, &free_list) {
+		psta = list_entry(plist, struct sta_info, auth_list);
+		list_del_init(&psta->auth_list);
+		rtw_free_stainfo(padapter, psta);
+	}
+
 	psta = NULL;
 
 	spin_lock_bh(&pstapriv->asoc_list_lock);
-- 
2.43.0

Re: [RFC PATCH] staging: rtl8723bs: fix potential race in expire_timeout_chk

[Greg KH]

On Tue, Jan 27, 2026 at 10:10:35PM +0900, Minu Jin wrote:
> The expire_timeout_chk function currently do lock and unlock inside the
> loop before calling rtw_free_stainfo().
> 
> This can be risky as the list might be changed
> when the lock is briefly released.
> 
> To fix this, move expired sta_info entries into a local free_list while
> holding the lock, and then perform the actual freeing after the lock is
> released.
> 
> Signed-off-by: Minu Jin <s9430939@naver.com>
> ---
> Hi,
> 
> I noticed this lock-unlock pattern in expire_timeout_chk() while
> studying the code and it looked like a potential race condition.
> 
> I've refactored the code to use a local list so we can handle the
> cleanup after releasing the lock. What do you think about this approach?
> 
> Any feedback is appreciated.
> 
>  drivers/staging/rtl8723bs/core/rtw_ap.c | 19 ++++++++++++-------
>  1 file changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/staging/rtl8723bs/core/rtw_ap.c b/drivers/staging/rtl8723bs/core/rtw_ap.c
> index 67197c7d4a4d..5947f6363ab0 100644
> --- a/drivers/staging/rtl8723bs/core/rtw_ap.c
> +++ b/drivers/staging/rtl8723bs/core/rtw_ap.c
> @@ -179,6 +179,9 @@ void expire_timeout_chk(struct adapter *padapter)
>  	u8 chk_alive_num = 0;
>  	char chk_alive_list[NUM_STA];
>  	int i;
> +	struct list_head free_list;
> +
> +	INIT_LIST_HEAD(&free_list);
>  
>  	spin_lock_bh(&pstapriv->auth_list_lock);
>  
> @@ -190,19 +193,21 @@ void expire_timeout_chk(struct adapter *padapter)
>  		if (psta->expire_to > 0) {
>  			psta->expire_to--;
>  			if (psta->expire_to == 0) {
> -				list_del_init(&psta->auth_list);
> +				list_move(&psta->auth_list, &free_list);
>  				pstapriv->auth_list_cnt--;
> -
> -				spin_unlock_bh(&pstapriv->auth_list_lock);
> -
> -				rtw_free_stainfo(padapter, psta);
> -
> -				spin_lock_bh(&pstapriv->auth_list_lock);
>  			}
>  		}
>  	}
>  
>  	spin_unlock_bh(&pstapriv->auth_list_lock);
> +
> +	/* free free_list */
> +	list_for_each_safe(plist, tmp, &free_list) {
> +		psta = list_entry(plist, struct sta_info, auth_list);
> +		list_del_init(&psta->auth_list);
> +		rtw_free_stainfo(padapter, psta);
> +	}

Looks sane, can you test it to verify it works properly?

thanks,

greg k-h

Re: [RFC PATCH] staging: rtl8723bs: fix potential race in expire_timeout_chk

[Minu Jin]

On Tue, Jan 27, 2026 at 03:15:24PM +0100, Greg KH wrote:
> On Tue, Jan 27, 2026 at 10:10:35PM +0900, Minu Jin wrote:
> > The expire_timeout_chk function currently do lock and unlock inside the
> > loop before calling rtw_free_stainfo().
> > 
> > This can be risky as the list might be changed
> > when the lock is briefly released.
> > 
> > To fix this, move expired sta_info entries into a local free_list while
> > holding the lock, and then perform the actual freeing after the lock is
> > released.
> > 
> > Signed-off-by: Minu Jin <s9430939@naver.com>
> > ---
> > Hi,
> > 
> > I noticed this lock-unlock pattern in expire_timeout_chk() while
> > studying the code and it looked like a potential race condition.
> > 
> > I've refactored the code to use a local list so we can handle the
> > cleanup after releasing the lock. What do you think about this approach?
> > 
> > Any feedback is appreciated.
> > 
> >  drivers/staging/rtl8723bs/core/rtw_ap.c | 19 ++++++++++++-------
> >  1 file changed, 12 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/staging/rtl8723bs/core/rtw_ap.c b/drivers/staging/rtl8723bs/core/rtw_ap.c
> > index 67197c7d4a4d..5947f6363ab0 100644
> > --- a/drivers/staging/rtl8723bs/core/rtw_ap.c
> > +++ b/drivers/staging/rtl8723bs/core/rtw_ap.c
> > @@ -179,6 +179,9 @@ void expire_timeout_chk(struct adapter *padapter)
> >  	u8 chk_alive_num = 0;
> >  	char chk_alive_list[NUM_STA];
> >  	int i;
> > +	struct list_head free_list;
> > +
> > +	INIT_LIST_HEAD(&free_list);
> >  
> >  	spin_lock_bh(&pstapriv->auth_list_lock);
> >  
> > @@ -190,19 +193,21 @@ void expire_timeout_chk(struct adapter *padapter)
> >  		if (psta->expire_to > 0) {
> >  			psta->expire_to--;
> >  			if (psta->expire_to == 0) {
> > -				list_del_init(&psta->auth_list);
> > +				list_move(&psta->auth_list, &free_list);
> >  				pstapriv->auth_list_cnt--;
> > -
> > -				spin_unlock_bh(&pstapriv->auth_list_lock);
> > -
> > -				rtw_free_stainfo(padapter, psta);
> > -
> > -				spin_lock_bh(&pstapriv->auth_list_lock);
> >  			}
> >  		}
> >  	}
> >  
> >  	spin_unlock_bh(&pstapriv->auth_list_lock);
> > +
> > +	/* free free_list */
> > +	list_for_each_safe(plist, tmp, &free_list) {
> > +		psta = list_entry(plist, struct sta_info, auth_list);
> > +		list_del_init(&psta->auth_list);
> > +		rtw_free_stainfo(padapter, psta);
> > +	}
> 
> Looks sane, can you test it to verify it works properly?
> 
> thanks,
> 
> greg k-h

Hi Greg,

Thanks for the review.

I have verified the patch with Smatch and performed build tests
it does not produce any errors or warnings.

About the runtime test,
I have analyzed the logic as follows:

Within the first loop, expired entries are simply moved to a local free_list.
Since we no longer release and re-acquire the lock inside this loop,
the integrity of the shared auth_list is perfectly preserved while iterating.

The actual cleanup (rtw_free_stainfo) is performed only after all entries
have been isolated into the local list and the lock has been released.

While I don't have the physical hardware to verify this myself,
I noticed that Hans de Goede has a working test environment for this driver.

I've added him to the CC list and would be very grateful
if he or anyone else with the hardware could give this a quick test.

Minu Jin

Re: [RFC PATCH] staging: rtl8723bs: fix potential race in expire_timeout_chk

[Dan Carpenter]

On Tue, Jan 27, 2026 at 10:10:35PM +0900, Minu Jin wrote:
> The expire_timeout_chk function currently do lock and unlock inside the
> loop before calling rtw_free_stainfo().
> 
> This can be risky as the list might be changed
> when the lock is briefly released.
> 
> To fix this, move expired sta_info entries into a local free_list while
> holding the lock, and then perform the actual freeing after the lock is
> released.
> 
> Signed-off-by: Minu Jin <s9430939@naver.com>
> ---
> Hi,
> 
> I noticed this lock-unlock pattern in expire_timeout_chk() while
> studying the code and it looked like a potential race condition.
> 
> I've refactored the code to use a local list so we can handle the
> cleanup after releasing the lock. What do you think about this approach?
> 
> Any feedback is appreciated.
> 
>  drivers/staging/rtl8723bs/core/rtw_ap.c | 19 ++++++++++++-------
>  1 file changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/staging/rtl8723bs/core/rtw_ap.c b/drivers/staging/rtl8723bs/core/rtw_ap.c
> index 67197c7d4a4d..5947f6363ab0 100644
> --- a/drivers/staging/rtl8723bs/core/rtw_ap.c
> +++ b/drivers/staging/rtl8723bs/core/rtw_ap.c
> @@ -179,6 +179,9 @@ void expire_timeout_chk(struct adapter *padapter)
>  	u8 chk_alive_num = 0;
>  	char chk_alive_list[NUM_STA];
>  	int i;
> +	struct list_head free_list;
> +
> +	INIT_LIST_HEAD(&free_list);

A couple minor style nits.  Use LIST_HEAD(free_list) to do this in the
initializer.

>  
>  	spin_lock_bh(&pstapriv->auth_list_lock);
>  
> @@ -190,19 +193,21 @@ void expire_timeout_chk(struct adapter *padapter)
>  		if (psta->expire_to > 0) {
>  			psta->expire_to--;
>  			if (psta->expire_to == 0) {
> -				list_del_init(&psta->auth_list);
> +				list_move(&psta->auth_list, &free_list);
>  				pstapriv->auth_list_cnt--;
> -
> -				spin_unlock_bh(&pstapriv->auth_list_lock);
> -
> -				rtw_free_stainfo(padapter, psta);
> -
> -				spin_lock_bh(&pstapriv->auth_list_lock);
>  			}
>  		}
>  	}
>  
>  	spin_unlock_bh(&pstapriv->auth_list_lock);
> +
> +	/* free free_list */

Delete this comment.  It's obvious.

> +	list_for_each_safe(plist, tmp, &free_list) {

Use list_for_each_entry_safe().

regards,
dan carpenter

> +		psta = list_entry(plist, struct sta_info, auth_list);
> +		list_del_init(&psta->auth_list);
> +		rtw_free_stainfo(padapter, psta);
> +	}
> +
>  	psta = NULL;