staging: rtl8723bs: fix OOB read in WMM_param_handler()

staging: rtl8723bs: fix OOB read in WMM_param_handler()

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>
Link: https://patch.msgid.link/20260719041509.97894-1-meatuni001@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>