wifi: rtl8xxxu: fix slab-out-of-bounds in rtl8xxxu_sta_add

commit 86c946b upstream.

The driver does not set hw->sta_data_size, which causes mac80211 to
allocate insufficient space for driver private station data in
__sta_info_alloc(). When rtl8xxxu_sta_add() accesses members of
struct rtl8xxxu_sta_info through sta->drv_priv, this results in a
slab-out-of-bounds write.

KASAN report on RISC-V (VisionFive 2) with RTL8192EU adapter:

  BUG: KASAN: slab-out-of-bounds in rtl8xxxu_sta_add+0x31c/0x346
  Write of size 8 at addr ffffffd6d3e9ae88 by task kworker/u16:0/12

Set hw->sta_data_size to sizeof(struct rtl8xxxu_sta_info) during
probe, similar to how hw->vif_data_size is configured. This ensures
mac80211 allocates sufficient space for the driver's per-station
private data.

Tested on StarFive VisionFive 2 v1.2A board.

Fixes: eef55f1 ("wifi: rtl8xxxu: support multiple interfaces in {add,remove}_interface()")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Tariq <alitariq45892@gmail.com>
Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20251225115430.13011-1-alitariq45892@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Ali Tariq

drivers/net/wireless/realtek/rtl8xxxu/core.c

@@ -7903,6 +7903,7 @@ static int rtl8xxxu_probe(struct usb_interface *interface,
 		goto err_set_intfdata;
 
 	hw->vif_data_size = sizeof(struct rtl8xxxu_vif);
+	hw->sta_data_size = sizeof(struct rtl8xxxu_sta_info);
 
 	hw->wiphy->max_scan_ssids = 1;
 	hw->wiphy->max_scan_ie_len = IEEE80211_MAX_DATA_LEN;