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core: rtw_ieee80211: guard attr_len underflow in rtw_get_p2p/wfd_attr_content #199

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core: rtw_ieee80211: guard attr_len underflow in rtw_get_p2p/wfd_attr_content #199

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18 changes: 16 additions & 2 deletions core/rtw_ieee80211.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2330,7 +2330,15 @@ u8 *rtw_get_p2p_attr_content(u8 *p2p_ie, uint p2p_ielen, u8 target_attr_id , u8

attr_ptr = rtw_get_p2p_attr(p2p_ie, p2p_ielen, target_attr_id, NULL, &attr_len);

if (attr_ptr && attr_len) {
/* attr_len includes the 3-byte attribute header (1 ID + 2 length).
* A malformed frame can yield attr_len < 3 (e.g. via u16 overflow in
* rtw_get_p2p_attr where attr_len = attr_data_len + 3 wraps when
* attr_data_len >= 0xFFFD). Without this guard, (attr_len - 3)
* underflows in u32 and the subsequent _rtw_memcpy() copies a huge
* length into buf_content -- which several callers pass as a
* fixed-size stack buffer (e.g. groupid[38], dev_addr[ETH_ALEN]).
*/
if (attr_ptr && attr_len >= 3) {
if (buf_content)
_rtw_memcpy(buf_content, attr_ptr + 3, attr_len - 3);

Expand Down Expand Up @@ -2728,7 +2736,13 @@ u8 *rtw_get_wfd_attr_content(u8 *wfd_ie, uint wfd_ielen, u8 target_attr_id, u8 *

attr_ptr = rtw_get_wfd_attr(wfd_ie, wfd_ielen, target_attr_id, NULL, &attr_len);

if (attr_ptr && attr_len) {
/* Same underflow guard as rtw_get_p2p_attr_content() above: attr_len
* carries the 3-byte WFD attribute header; a malformed frame can
* yield attr_len < 3 (parser's u16 (attr_data_len + 3) wraps when
* attr_data_len >= 0xFFFD). Without the >= 3 check, (attr_len - 3)
* underflows in u32 and the memcpy() copies a huge length.
*/
if (attr_ptr && attr_len >= 3) {
if (buf_content)
_rtw_memcpy(buf_content, attr_ptr + 3, attr_len - 3);

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