[PATCH v9] staging: rtl8723bs: fix WEP length underflow and OOB read in OnAuth()

[PATCH v9] staging: rtl8723bs: fix WEP length underflow and OOB read in OnAuth()

[Alexandru Hossu]

OnAuth() has two bugs in the shared-key authentication path.

When the Privacy bit is set, rtw_wep_decrypt() is called without
verifying that the frame is long enough to contain a valid WEP IV and
ICV.  Inside rtw_wep_decrypt(), length is computed as:

    length = len - WLAN_HDR_A3_LEN - iv_len

and then passed as (length - 4) to crc32_le().  If len is less than
WLAN_HDR_A3_LEN + iv_len + icv_len (32 bytes), length - 4 is negative
and, after the implicit cast to size_t, causes crc32_le() to read far
beyond the frame buffer.  Add a minimum length check before accessing
the IV field and calling the decryption path.

When processing a seq=3 response, rtw_get_ie() stores the Challenge
Text IE length in ie_len, but the subsequent memcmp() always reads 128
bytes regardless of ie_len.  IEEE 802.11 mandates a challenge text of
exactly 128 bytes; reject any IE whose length field differs, matching
the check already applied to OnAuthClient().

Fixes: 554c0a3abf21 ("staging: Add rtl8723bs sdio wifi driver")
Cc: stable@vger.kernel.org
Signed-off-by: Alexandru Hossu <hossu.alexandru@gmail.com>
---
v9: add WLAN_HDR_A3_LEN guard and WEP minimum length check before
    iv[3] access and rtw_wep_decrypt(); tighten ie_len check from
    <= 0 to != 128 to reject under-size challenge IEs

 drivers/staging/rtl8723bs/core/rtw_mlme_ext.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c b/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
index 68ce422305ed..8575b7bd6d84 100644
--- a/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
+++ b/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
@@ -687,6 +687,9 @@ unsigned int OnAuth(struct adapter *padapter, union recv_frame *precv_frame)
 	if ((pmlmeinfo->state&0x03) != WIFI_FW_AP_STATE)
 		return _FAIL;
 
+	if (len < WLAN_HDR_A3_LEN)
+		return _FAIL;
+
 	sa = GetAddr2Ptr(pframe);
 
 	auth_mode = psecuritypriv->dot11AuthAlgrthm;
@@ -698,6 +701,9 @@ unsigned int OnAuth(struct adapter *padapter, union recv_frame *precv_frame)
 		prxattrib->hdrlen = WLAN_HDR_A3_LEN;
 		prxattrib->encrypt = _WEP40_;
 
+		if (len < WLAN_HDR_A3_LEN + 8)
+			return _FAIL;
+
 		iv = pframe+prxattrib->hdrlen;
 		prxattrib->key_index = ((iv[3]>>6)&0x3);
 
@@ -802,7 +808,7 @@ unsigned int OnAuth(struct adapter *padapter, union recv_frame *precv_frame)
 			p = rtw_get_ie(pframe + WLAN_HDR_A3_LEN + 4 + _AUTH_IE_OFFSET_, WLAN_EID_CHALLENGE, (int *)&ie_len,
 					len - WLAN_HDR_A3_LEN - _AUTH_IE_OFFSET_ - 4);
 
-			if (!p || ie_len <= 0) {
+			if (!p || ie_len != 128) {
 				status = WLAN_STATUS_CHALLENGE_FAIL;
 				goto auth_fail;
 			}
-- 
2.54.0

Re: [PATCH v9] staging: rtl8723bs: fix WEP length underflow and OOB read in OnAuth()

[Greg KH]

On Thu, May 21, 2026 at 03:03:24PM +0200, Alexandru Hossu wrote:
> OnAuth() has two bugs in the shared-key authentication path.
> 
> When the Privacy bit is set, rtw_wep_decrypt() is called without
> verifying that the frame is long enough to contain a valid WEP IV and
> ICV.  Inside rtw_wep_decrypt(), length is computed as:
> 
>     length = len - WLAN_HDR_A3_LEN - iv_len
> 
> and then passed as (length - 4) to crc32_le().  If len is less than
> WLAN_HDR_A3_LEN + iv_len + icv_len (32 bytes), length - 4 is negative
> and, after the implicit cast to size_t, causes crc32_le() to read far
> beyond the frame buffer.  Add a minimum length check before accessing
> the IV field and calling the decryption path.
> 
> When processing a seq=3 response, rtw_get_ie() stores the Challenge
> Text IE length in ie_len, but the subsequent memcmp() always reads 128
> bytes regardless of ie_len.  IEEE 802.11 mandates a challenge text of
> exactly 128 bytes; reject any IE whose length field differs, matching
> the check already applied to OnAuthClient().
> 
> Fixes: 554c0a3abf21 ("staging: Add rtl8723bs sdio wifi driver")
> Cc: stable@vger.kernel.org
> Signed-off-by: Alexandru Hossu <hossu.alexandru@gmail.com>
> ---
> v9: add WLAN_HDR_A3_LEN guard and WEP minimum length check before
>     iv[3] access and rtw_wep_decrypt(); tighten ie_len check from
>     <= 0 to != 128 to reject under-size challenge IEs
> 
>  drivers/staging/rtl8723bs/core/rtw_mlme_ext.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c b/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
> index 68ce422305ed..8575b7bd6d84 100644
> --- a/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
> +++ b/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
> @@ -687,6 +687,9 @@ unsigned int OnAuth(struct adapter *padapter, union recv_frame *precv_frame)
>  	if ((pmlmeinfo->state&0x03) != WIFI_FW_AP_STATE)
>  		return _FAIL;
>  
> +	if (len < WLAN_HDR_A3_LEN)
> +		return _FAIL;
> +
>  	sa = GetAddr2Ptr(pframe);
>  
>  	auth_mode = psecuritypriv->dot11AuthAlgrthm;
> @@ -698,6 +701,9 @@ unsigned int OnAuth(struct adapter *padapter, union recv_frame *precv_frame)
>  		prxattrib->hdrlen = WLAN_HDR_A3_LEN;
>  		prxattrib->encrypt = _WEP40_;
>  
> +		if (len < WLAN_HDR_A3_LEN + 8)
> +			return _FAIL;
> +
>  		iv = pframe+prxattrib->hdrlen;
>  		prxattrib->key_index = ((iv[3]>>6)&0x3);
>  
> @@ -802,7 +808,7 @@ unsigned int OnAuth(struct adapter *padapter, union recv_frame *precv_frame)
>  			p = rtw_get_ie(pframe + WLAN_HDR_A3_LEN + 4 + _AUTH_IE_OFFSET_, WLAN_EID_CHALLENGE, (int *)&ie_len,
>  					len - WLAN_HDR_A3_LEN - _AUTH_IE_OFFSET_ - 4);
>  
> -			if (!p || ie_len <= 0) {
> +			if (!p || ie_len != 128) {
>  				status = WLAN_STATUS_CHALLENGE_FAIL;
>  				goto auth_fail;
>  			}
> -- 
> 2.54.0
> 
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

You are receiving this message because of the following common error(s)
as indicated below:


- This looks like a new version of a previously submitted patch, but you
  did not list below the --- line any changes from the previous version.
  Please read the section entitled "The canonical patch format" in the
  kernel file, Documentation/process/submitting-patches.rst for what
  needs to be done here to properly describe this.


If you wish to discuss this problem further, or you have questions about
how to resolve this issue, please feel free to respond to this email and
Greg will reply once he has dug out from the pending patches received
from other developers.

thanks,

greg k-h's patch email bot

[PATCH v10] staging: rtl8723bs: fix WEP length underflow and OOB read in OnAuth()

[Alexandru Hossu]

OnAuth() has two bugs in the shared-key authentication path.

When the Privacy bit is set, rtw_wep_decrypt() is called without
verifying that the frame is long enough to contain a valid WEP IV and
ICV.  Inside rtw_wep_decrypt(), length is computed as:

    length = len - WLAN_HDR_A3_LEN - iv_len

and then passed as (length - 4) to crc32_le().  If len is less than
WLAN_HDR_A3_LEN + iv_len + icv_len (32 bytes), length - 4 is negative
and, after the implicit cast to size_t, causes crc32_le() to read far
beyond the frame buffer.  Add a minimum length check before accessing
the IV field and calling the decryption path.

When processing a seq=3 response, rtw_get_ie() stores the Challenge
Text IE length in ie_len, but the subsequent memcmp() always reads 128
bytes regardless of ie_len.  IEEE 802.11 mandates a challenge text of
exactly 128 bytes; reject any IE whose length field differs, matching
the check already applied to OnAuthClient().

Fixes: 554c0a3abf21 ("staging: Add rtl8723bs sdio wifi driver")
Cc: stable@vger.kernel.org
Signed-off-by: Alexandru Hossu <hossu.alexandru@gmail.com>
---
v10: no code changes; add full version history below --- (omitted from v9)
v9: add WLAN_HDR_A3_LEN guard and WEP minimum length check before
    iv[3] access and rtw_wep_decrypt(); tighten ie_len check from
    <= 0 to != 128 to reject under-size challenge IEs
v8: standalone patch; change WLAN_HDR_A3_LEN early exit to return _FAIL
    (sa not yet initialised at that point, goto auth_fail would copy
    garbage into the rejection frame's destination address); add guard
    for iv[3] read inside GetPrivacy() branch (len < WLAN_HDR_A3_LEN +
    4); set status = WLAN_STATUS_UNSPECIFIED_FAILURE before goto auth_fail
v7: initial OnAuth fix (sent as [PATCH v7 0/2] 2/2); add frame length
    guards before GetAddr2Ptr() and before algorithm/seq reads; correct
    commit message (rtw_get_ie() uses signed int limit and returns NULL
    when limit < 2, so the unsigned underflow OOB scan claimed in earlier
    versions cannot occur)

v9: https://lore.kernel.org/r/20260521130324.754100-1-hossu.alexandru@gmail.com
v8: https://lore.kernel.org/r/20260511185314.1625375-1-hossu.alexandru@gmail.com
v7: https://lore.kernel.org/r/20260505211316.3837020-1-hossu.alexandru@gmail.com

 drivers/staging/rtl8723bs/core/rtw_mlme_ext.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c b/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
index 68ce422305ed..8575b7bd6d84 100644
--- a/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
+++ b/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
@@ -687,6 +687,9 @@ unsigned int OnAuth(struct adapter *padapter, union recv_frame *precv_frame)
 	if ((pmlmeinfo->state&0x03) != WIFI_FW_AP_STATE)
 		return _FAIL;

+	if (len < WLAN_HDR_A3_LEN)
+		return _FAIL;
+
 	sa = GetAddr2Ptr(pframe);

 	auth_mode = psecuritypriv->dot11AuthAlgrthm;
@@ -698,6 +701,9 @@ unsigned int OnAuth(struct adapter *padapter, union recv_frame *precv_frame)
 		prxattrib->hdrlen = WLAN_HDR_A3_LEN;
 		prxattrib->encrypt = _WEP40_;

+		if (len < WLAN_HDR_A3_LEN + 8)
+			return _FAIL;
+
 		iv = pframe+prxattrib->hdrlen;
 		prxattrib->key_index = ((iv[3]>>6)&0x3);

@@ -802,7 +808,7 @@ unsigned int OnAuth(struct adapter *padapter, union recv_frame *precv_frame)
 			p = rtw_get_ie(pframe + WLAN_HDR_A3_LEN + 4 + _AUTH_IE_OFFSET_, WLAN_EID_CHALLENGE, (int *)&ie_len,
 					len - WLAN_HDR_A3_LEN - _AUTH_IE_OFFSET_ - 4);

-			if (!p || ie_len <= 0) {
+			if (!p || ie_len != 128) {
 				status = WLAN_STATUS_CHALLENGE_FAIL;
 				goto auth_fail;
 			}
--
2.54.0