[PATCH 1/2] staging: rtl8723bs: fix OOB write in HT_caps_handler()

[PATCH 1/2] staging: rtl8723bs: fix OOB write in HT_caps_handler()

[Alexandru Hossu]

From: Alexandru Hossu <a.hossu@student.tudelft.nl>

HT_caps_handler() iterates pIE->length bytes and writes into
HT_caps.u.HT_cap[], which is a fixed 26-byte array (sizeof struct
HT_caps_element).  Because pIE->length is a raw u8 from an over-the-air
802.11 AssocResponse frame and is never validated, a malicious AP can set
it up to 255, causing up to 229 bytes of out-of-bounds writes into
adjacent fields of struct mlme_ext_info.

The parallel function HT_info_handler() already carries the correct guard:

  if (pIE->length > sizeof(struct HT_info_element))
          return;

Apply the same pattern to HT_caps_handler().

Signed-off-by: Alexandru Hossu <a.hossu@student.tudelft.nl>
---
 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 6a7c09db4..b75e7f4f8 100644
--- a/drivers/staging/rtl8723bs/core/rtw_wlan_util.c
+++ b/drivers/staging/rtl8723bs/core/rtw_wlan_util.c
@@ -934,6 +934,9 @@ void HT_caps_handler(struct adapter *padapter, struct ndis_80211_var_ie *pIE)
 	if (phtpriv->ht_option == false)
 		return;
 
+	if (pIE->length > sizeof(struct HT_caps_element))
+		return;
+
 	pmlmeinfo->HT_caps_enable = 1;
 
 	for (i = 0; i < (pIE->length); i++) {
-- 
2.53.0

[PATCH 2/2] staging: rtl8723bs: fix OOB read in OnAssocRsp() IE loop

[Alexandru Hossu]

From: Alexandru Hossu <a.hossu@student.tudelft.nl>

The IE parsing loop in OnAssocRsp() advances by (pIE->length + 2) each
iteration but only guards on i < pkt_len.  When a malicious AP sends an
AssocResponse whose last IE has only one byte remaining in the frame (the
element_id byte lands at pkt_len-1), the loop reads pIE->length from
pframe[pkt_len], which is one byte past the allocated receive buffer.

Additionally, even when the header bytes are in bounds, pIE->length itself
can extend the data window beyond pkt_len, silently passing a truncated IE
to the handler functions.

Add two guards at the top of the loop body:
  1. Break if fewer than sizeof(*pIE) bytes remain (can't read the header).
  2. Break if the IE's declared data extends past pkt_len.

Signed-off-by: Alexandru Hossu <a.hossu@student.tudelft.nl>
---
 drivers/staging/rtl8723bs/core/rtw_mlme_ext.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c b/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
index 5f00fe282..9666226a6 100644
--- a/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
+++ b/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
@@ -1400,7 +1400,11 @@ unsigned int OnAssocRsp(struct adapter *padapter, union recv_frame *precv_frame)
 	/* to handle HT, WMM, rate adaptive, update MAC reg */
 	/* for not to handle the synchronous IO in the tasklet */
 	for (i = (6 + WLAN_HDR_A3_LEN); i < pkt_len;) {
+		if (i + sizeof(*pIE) > pkt_len)
+			break;
 		pIE = (struct ndis_80211_var_ie *)(pframe + i);
+		if (i + sizeof(*pIE) + pIE->length > pkt_len)
+			break;
 
 		switch (pIE->element_id) {
 		case WLAN_EID_VENDOR_SPECIFIC:
-- 
2.53.0

Re: [PATCH 1/2] staging: rtl8723bs: fix OOB write in HT_caps_handler()

[Alexandru Hossu]

Sorry for the noise — the previous series was sent with the wrong
From/Signed-off-by (university address instead of personal Gmail).
Please ignore patches 1/2 and 2/2 from Message-ID
<20260420140432.150431-1-hossu.alexandru@gmail.com>.
Resending the correct series now.

Alexandru

[PATCH 1/2] staging: rtl8723bs: fix OOB write in HT_caps_handler()

[Alexandru Hossu]

HT_caps_handler() iterates pIE->length bytes and writes into
HT_caps.u.HT_cap[], which is a fixed 26-byte array (sizeof struct
HT_caps_element).  Because pIE->length is a raw u8 from an over-the-air
802.11 AssocResponse frame and is never validated, a malicious AP can set
it up to 255, causing up to 229 bytes of out-of-bounds writes into
adjacent fields of struct mlme_ext_info.

The parallel function HT_info_handler() already carries the correct guard:

  if (pIE->length > sizeof(struct HT_info_element))
          return;

Apply the same pattern to HT_caps_handler().

Signed-off-by: Alexandru Hossu <hossu.alexandru@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 6a7c09db4..b75e7f4f8 100644
--- a/drivers/staging/rtl8723bs/core/rtw_wlan_util.c
+++ b/drivers/staging/rtl8723bs/core/rtw_wlan_util.c
@@ -934,6 +934,9 @@ void HT_caps_handler(struct adapter *padapter, struct ndis_80211_var_ie *pIE)
 	if (phtpriv->ht_option == false)
 		return;
 
+	if (pIE->length > sizeof(struct HT_caps_element))
+		return;
+
 	pmlmeinfo->HT_caps_enable = 1;
 
 	for (i = 0; i < (pIE->length); i++) {
-- 
2.53.0

Re: [PATCH 1/2] staging: rtl8723bs: fix OOB write in HT_caps_handler()

[Luka Gejak]

On Mon Apr 20, 2026 at 4:08 PM CEST, Alexandru Hossu wrote:
> HT_caps_handler() iterates pIE->length bytes and writes into
> HT_caps.u.HT_cap[], which is a fixed 26-byte array (sizeof struct
> HT_caps_element).  Because pIE->length is a raw u8 from an over-the-air
> 802.11 AssocResponse frame and is never validated, a malicious AP can set
> it up to 255, causing up to 229 bytes of out-of-bounds writes into
> adjacent fields of struct mlme_ext_info.
>
> The parallel function HT_info_handler() already carries the correct guard:
>
>   if (pIE->length > sizeof(struct HT_info_element))
>           return;
>
> Apply the same pattern to HT_caps_handler().
>
> Signed-off-by: Alexandru Hossu <hossu.alexandru@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 6a7c09db4..b75e7f4f8 100644
> --- a/drivers/staging/rtl8723bs/core/rtw_wlan_util.c
> +++ b/drivers/staging/rtl8723bs/core/rtw_wlan_util.c
> @@ -934,6 +934,9 @@ void HT_caps_handler(struct adapter *padapter, struct ndis_80211_var_ie *pIE)
>  	if (phtpriv->ht_option == false)
>  		return;
>  
> +	if (pIE->length > sizeof(struct HT_caps_element))
> +		return;
> +
>  	pmlmeinfo->HT_caps_enable = 1;
>  
>  	for (i = 0; i < (pIE->length); i++) {

Hi Alexandru,
this fix has been made already by Greg HK therefore this patch is 
unnecessary. You can see his patch at [1].
Best regards,
Luka Gejak

[1]: https://lore.kernel.org/linux-staging/2026041408-grill-mahogany-d1e3@gregkh/

Re: [PATCH 1/2] staging: rtl8723bs: fix OOB write in HT_caps_handler()

[Luka Gejak]

On Tue Apr 21, 2026 at 4:40 PM CEST, Luka Gejak wrote:
> On Mon Apr 20, 2026 at 4:08 PM CEST, Alexandru Hossu wrote:
>> HT_caps_handler() iterates pIE->length bytes and writes into
>> HT_caps.u.HT_cap[], which is a fixed 26-byte array (sizeof struct
>> HT_caps_element).  Because pIE->length is a raw u8 from an over-the-air
>> 802.11 AssocResponse frame and is never validated, a malicious AP can set
>> it up to 255, causing up to 229 bytes of out-of-bounds writes into
>> adjacent fields of struct mlme_ext_info.
>>
>> The parallel function HT_info_handler() already carries the correct guard:
>>
>>   if (pIE->length > sizeof(struct HT_info_element))
>>           return;
>>
>> Apply the same pattern to HT_caps_handler().
>>
>> Signed-off-by: Alexandru Hossu <hossu.alexandru@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 6a7c09db4..b75e7f4f8 100644
>> --- a/drivers/staging/rtl8723bs/core/rtw_wlan_util.c
>> +++ b/drivers/staging/rtl8723bs/core/rtw_wlan_util.c
>> @@ -934,6 +934,9 @@ void HT_caps_handler(struct adapter *padapter, struct ndis_80211_var_ie *pIE)
>>  	if (phtpriv->ht_option == false)
>>  		return;
>>  
>> +	if (pIE->length > sizeof(struct HT_caps_element))
>> +		return;
>> +
>>  	pmlmeinfo->HT_caps_enable = 1;
>>  
>>  	for (i = 0; i < (pIE->length); i++) {
>
> Hi Alexandru,
> this fix has been made already by Greg HK therefore this patch is 
					^^^^ *KH (Kroah-Hartman)
> unnecessary. You can see his patch at [1].
> Best regards,
> Luka Gejak
>
> [1]: https://lore.kernel.org/linux-staging/2026041408-grill-mahogany-d1e3@gregkh/