staging: rtl8723bs: Drop get_recvframe_data()

When building with -Warray-bounds, the following warning is emitted:

In file included from ./include/linux/string.h:253,
from ./arch/x86/include/asm/page_32.h:22,
from ./arch/x86/include/asm/page.h:14,
from ./arch/x86/include/asm/thread_info.h:12,
from ./include/linux/thread_info.h:60,
from ./arch/x86/include/asm/preempt.h:7,
from ./include/linux/preempt.h:78,
from ./include/linux/rcupdate.h:27,
from ./include/linux/rculist.h:11,
from ./include/linux/sched/signal.h:5,
from ./drivers/staging/rtl8723bs/include/drv_types.h:17,
from drivers/staging/rtl8723bs/core/rtw_recv.c:7:
In function 'memcpy',
inlined from 'wlanhdr_to_ethhdr' at drivers/staging/rtl8723bs/core/rtw_recv.c:1554:2:
./include/linux/fortify-string.h:41:33: warning: '__builtin_memcpy' offset [0, 5] is out of the bounds [0, 0] [-Warray-bounds]
41 | #define __underlying_memcpy __builtin_memcpy
| ^

This is because the compiler sees it is possible for "ptr" to be a NULL
value, and concludes that it has zero size and attempts to copy to it
would overflow. Instead, remove the get_recvframe_data() entirely, as
it's not possible for this to ever be NULL.

Additionally add missing NULL checks after recvframe_pull() (which are
present in the rtl8712 driver).

Cc: Larry Finger <[e-mail]>
Cc: Phillip Potter <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Cc: Michael Straube <[e-mail]>
Cc: Fabio Aiuto <[e-mail]>
Cc: [e-mail]
Reviewed-by: Hans de Goede <[e-mail]>
Signed-off-by: Kees Cook <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/rtl8723bs/core/rtw_recv.c

···
 
 	auth_alg = adapter->securitypriv.dot11AuthAlgrthm;
 
-	ptr = get_recvframe_data(precv_frame);
+	ptr = precv_frame->u.hdr.rx_data;
 	pfhdr = &precv_frame->u.hdr;
 	pattrib = &pfhdr->attrib;
 	psta_addr = pattrib->ta;
···
 	__be16 be_tmp;
 	struct adapter			*adapter = precvframe->u.hdr.adapter;
 	struct mlme_priv *pmlmepriv = &adapter->mlmepriv;
-	u8 *ptr = get_recvframe_data(precvframe) ; /*  point to frame_ctrl field */
+	u8 *ptr = precvframe->u.hdr.rx_data; /*  point to frame_ctrl field */
 	struct rx_pkt_attrib *pattrib = &precvframe->u.hdr.attrib;
 
 	if (pattrib->encrypt)
···
 		eth_type = 0x8712;
 		/*  append rx status for mp test packets */
 		ptr = recvframe_pull(precvframe, (rmv_len-sizeof(struct ethhdr)+2)-24);
+		if (!ptr)
+			return _FAIL;
 		memcpy(ptr, get_rxmem(precvframe), 24);
 		ptr += 24;
-	} else
+	} else {
 		ptr = recvframe_pull(precvframe, (rmv_len-sizeof(struct ethhdr) + (bsnaphdr?2:0)));
+		if (!ptr)
+			return _FAIL;
+	}
 
 	memcpy(ptr, pattrib->dst, ETH_ALEN);
 	memcpy(ptr+ETH_ALEN, pattrib->src, ETH_ALEN);

drivers/staging/rtl8723bs/hal/rtl8723bs_recv.c

···
 	struct odm_phy_info *p_phy_info =
 		(struct odm_phy_info *)(&pattrib->phy_info);
 
-	u8 *wlanhdr;
+	u8 *wlanhdr = precvframe->u.hdr.rx_data;
 	u8 *my_bssid;
 	u8 *rx_bssid;
 	u8 *rx_ra;
···
 	struct sta_priv *pstapriv;
 	struct sta_info *psta;
 
-	wlanhdr = get_recvframe_data(precvframe);
 	my_bssid = get_bssid(&padapter->mlmepriv);
 	rx_bssid = get_hdr_bssid(wlanhdr);
 	pkt_info.bssid_match = ((!IsFrameTypeCtrl(wlanhdr)) &&

drivers/staging/rtl8723bs/include/rtw_recv.h

···
 	return precvframe->u.hdr.rx_head;
 }
 
-static inline u8 *get_recvframe_data(union recv_frame *precvframe)
-{
-
-	/* alwasy return rx_data */
-	if (precvframe == NULL)
-		return NULL;
-
-	return precvframe->u.hdr.rx_data;
-
-}
-
 static inline u8 *recvframe_pull(union recv_frame *precvframe, signed int sz)
 {
 	/*  rx_data += sz; move rx_data sz bytes  hereafter */