[PATCH] staging: rtl8723bs: fix OOB read in WMM_param_handler()

[Muhammad Bilal <meatuni001@gmail.com>]

WMM_param_handler() copies a fixed-size WMM parameter element out of a
received information element without checking that the element is long
enough, causing an out-of-bounds read for a short WMM IE.

The handler reads sizeof(struct WMM_para_element) (18) bytes at
pIE->data + 6, so it requires pIE->length to be at least 24
(WLAN_WMM_LEN), but it never validates the length. Two of its three
callers reach it after matching only the WMM OUI: OnAssocRsp() in
rtw_mlme_ext.c matches a 6-byte OUI, and join_cmd_hdl() matches a
4-byte OUI, before calling the handler. A vendor-specific IE carrying
the WMM OUI but a length between 6 and 23, placed in an association
response or in the IE blob handed to join_cmd_hdl(), passes the OUI
check and then makes the memcmp() and memcpy() at pIE->data + 6 read
past the end of the element. OnAssocRsp() parses a frame received from
the AP, so this is reachable from a remote peer.

The remaining caller in rtw_wlan_util.c already guards the handler with
"pIE->length == WLAN_WMM_LEN". Move the equivalent check into the
handler itself so every caller is covered; the sibling IE handlers in
the same parsing loop (HT_caps_handler(), HT_info_handler(),
ERP_IE_handler()) likewise bound their accesses by pIE->length.

Fixes: 554c0a3abf21 ("staging: Add rtl8723bs sdio wifi driver")
Cc: stable@vger.kernel.org
Signed-off-by: Muhammad Bilal <meatuni001@gmail.com>
---
 drivers/staging/rtl8723bs/core/rtw_wlan_util.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/staging/rtl8723bs/core/rtw_wlan_util.c b/drivers/staging/rtl8723bs/core/rtw_wlan_util.c
index a4de538722b5..c614c0b4c792 100644
--- a/drivers/staging/rtl8723bs/core/rtw_wlan_util.c
+++ b/drivers/staging/rtl8723bs/core/rtw_wlan_util.c
@@ -666,6 +666,9 @@ int WMM_param_handler(struct adapter *padapter, struct ndis_80211_var_ie *pIE)
 		return false;
 	}
 
+	if (pIE->length != WLAN_WMM_LEN)
+		return false;
+
 	if (!memcmp(&(pmlmeinfo->WMM_param), (pIE->data + 6), sizeof(struct WMM_para_element)))
 		return false;
 
-- 
2.55.0