Commit c6dd3071 authored by Martin Kaiser's avatar Martin Kaiser Committed by Greg Kroah-Hartman
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staging: r8188eu: clean up NULL check for rcu pointer 



Clean up the NULL check for padapter->pnetdev->rx_handler_data.

The current code calls rcu_dereference while it holds the rcu read lock
and checks the pointer after releasing the lock. An rcu pointer may only be
used between calls to rcu_read_lock and rcu_read_unlock.

Replace the check with rcu_access_pointer. My understanding is that this
function returns the value of the pointer and needs no locking. We can
then check the pointer but we must not dereference it.

Signed-off-by: default avatarMartin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20230131090057.241779-1-martin@kaiser.cx


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 7f0c1244

drivers/staging/r8188eu/core/rtw_xmit.c

+2 −6
Original line number Diff line number Diff line
@@ -1631,18 +1631,14 @@ s32 rtw_xmit(struct adapter *padapter, struct sk_buff **ppkt) 
	struct xmit_priv *pxmitpriv = &padapter->xmitpriv;

	struct xmit_frame *pxmitframe = NULL;

	struct mlme_priv	*pmlmepriv = &padapter->mlmepriv;

	void *br_port = NULL;

	s32 res;



	pxmitframe = rtw_alloc_xmitframe(pxmitpriv);

	if (!pxmitframe)

		return -1;



	rcu_read_lock();

	br_port = rcu_dereference(padapter->pnetdev->rx_handler_data);

	rcu_read_unlock();



	if (br_port && check_fwstate(pmlmepriv, WIFI_STATION_STATE | WIFI_ADHOC_STATE)) {

	if (rcu_access_pointer(padapter->pnetdev->rx_handler_data) &&

	    check_fwstate(pmlmepriv, WIFI_STATION_STATE | WIFI_ADHOC_STATE)) {

		res = rtw_br_client_tx(padapter, ppkt);

		if (res == -1) {

			rtw_free_xmitframe(pxmitpriv, pxmitframe);