linux-kernel - [PATCH v2 2/2] staging: rtl8192e: Change state information from u16 to u8

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Date:   Tue, 23 Mar 2021 17:04:14 +0530
From:   Atul Gopinathan <atulgopinathan@...il.com>
To:     gregkh@...uxfoundation.org
Cc:     linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org,
        skhan@...uxfoundation.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Atul Gopinathan <atulgopinathan@...il.com>,
        stable@...r.kernel.org
Subject: [PATCH v2 2/2] staging: rtl8192e: Change state information from u16 to u8

The "u16 CcxRmState[2];" array field in struct "rtllib_network" has 4
bytes in total while the operations performed on this array through-out
the code base are only 2 bytes.

The "CcxRmState" field is fed only 2 bytes of data using memcpy():

(In rtllib_rx.c:1972)
	memcpy(network->CcxRmState, &info_element->data[4], 2)

With "info_element->data[]" being a u8 array, if 2 bytes are written
into "CcxRmState" (whose one element is u16 size), then the 2 u8
elements from "data[]" gets squashed and written into the first element
("CcxRmState[0]") while the second element ("CcxRmState[1]") is never
fed with any data.

Same in file rtllib_rx.c:2522:
	 memcpy(dst->CcxRmState, src->CcxRmState, 2);

The above line duplicates "src" data to "dst" but only writes 2 bytes
(and not 4, which is the actual size). Again, only 1st element gets the
value while the 2nd element remains uninitialized.

This later makes operations done with CcxRmState unpredictable in the
following lines as the 1st element is having a squashed number while the
2nd element is having an uninitialized random number.

rtllib_rx.c:1973:    if (network->CcxRmState[0] != 0)
rtllib_rx.c:1977:    network->MBssidMask = network->CcxRmState[1] & 0x07;

network->MBssidMask is also of type u8 and not u16.

Fix this by changing the type of "CcxRmState" from u16 to u8 so that the
data written into this array and read from it make sense and are not
random values.

NOTE: The wrong initialization of "CcxRmState" can be seen in the
following commit:

commit ecdfa44610fa ("Staging: add Realtek 8192 PCI wireless driver")

The above commit created a file `rtl8192e/ieee80211.h` which used to
have the faulty line. The file has been deleted (or possibly renamed)
with the contents copied in to a new file `rtl8192e/rtllib.h` along with
additional code in the commit 94a799425eee (tagged in Fixes).

Fixes: 94a799425eee ("[PATCH 1/8] rtl8192e: Import new version of driver from realtek")
Cc: stable@...r.kernel.org
Signed-off-by: Atul Gopinathan <atulgopinathan@...il.com>
---
 drivers/staging/rtl8192e/rtllib.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/rtl8192e/rtllib.h b/drivers/staging/rtl8192e/rtllib.h
index b84f00b8d18b..4cabaf21c1ca 100644
--- a/drivers/staging/rtl8192e/rtllib.h
+++ b/drivers/staging/rtl8192e/rtllib.h
@@ -1101,15 +1101,15 @@ struct rtllib_network {
 	u8 hidden_ssid[IW_ESSID_MAX_SIZE + 1];
 	u8 hidden_ssid_len;
 	struct rtllib_qos_data qos_data;

 	bool	bWithAironetIE;
 	bool	bCkipSupported;
 	bool	bCcxRmEnable;
-	u16	CcxRmState[2];
+	u8	CcxRmState[2];
 	bool	bMBssidValid;
 	u8	MBssidMask;
 	u8	MBssid[ETH_ALEN];
 	bool	bWithCcxVerNum;
 	u8	BssCcxVerNumber;
 	/* These are network statistics */
 	struct rtllib_rx_stats stats;
-- 
2.25.1