[PATCH] staging: rtl8723bs: fix heap overflow in OnAuthClient shared key path

[Alexandru Hossu <hossu.alexandru@gmail.com>]

rtw_get_ie() returns the raw IE length from the received frame, which
can be up to 255. This length is used directly in memcpy() into
chg_txt[128] with no bounds check, allowing a heap overflow of up to
127 bytes when a rogue AP sends an Auth seq=2 frame with a Challenge
Text IE longer than 128 bytes.

IEEE 802.11 mandates the Challenge Text element carries exactly 128
bytes of challenge data. Reject any element whose length field does not
match sizeof(pmlmeinfo->chg_txt) (128).

Fixes: 554c0a3abf21 ("staging: Add rtl8723bs sdio wifi driver")
Cc: stable@vger.kernel.org
Signed-off-by: Alexandru Hossu <hossu.alexandru@gmail.com>
---
 drivers/staging/rtl8723bs/core/rtw_mlme_ext.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c b/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
index 5f00fe282d1b..90f27665667a 100644
--- a/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
+++ b/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
@@ -891,7 +891,7 @@ unsigned int OnAuthClient(struct adapter *padapter, union recv_frame *precv_fram
 			p = rtw_get_ie(pframe + WLAN_HDR_A3_LEN + _AUTH_IE_OFFSET_, WLAN_EID_CHALLENGE, (int *)&len,
 				pkt_len - WLAN_HDR_A3_LEN - _AUTH_IE_OFFSET_);
 
-			if (!p)
+			if (!p || len != sizeof(pmlmeinfo->chg_txt))
 				goto authclnt_fail;
 
 			memcpy(pmlmeinfo->chg_txt, p + 2, len);
-- 
2.53.0