From b870e73a56c4cccbec33224233eaf295839f228c Mon Sep 17 00:00:00 2001
From: Szymon Heidrich <szymon.heidrich@gmail.com>
Date: Wed, 11 Jan 2023 18:50:31 +0100
Subject: [PATCH] wifi: rndis_wlan: Prevent buffer overflow in rndis_query_oid
Git-commit: b870e73a56c4cccbec33224233eaf295839f228c
Patch-mainline: v6.2-rc5
References: git-fixes

Since resplen and respoffs are signed integers sufficiently
large values of unsigned int len and offset members of RNDIS
response will result in negative values of prior variables.
This may be utilized to bypass implemented security checks
to either extract memory contents by manipulating offset or
overflow the data buffer via memcpy by manipulating both
offset and len.

Additionally assure that sum of resplen and respoffs does not
overflow so buffer boundaries are kept.

Fixes: 80f8c5b434f9 ("rndis_wlan: copy only useful data from rndis_command respond")
Signed-off-by: Szymon Heidrich <szymon.heidrich@gmail.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230111175031.7049-1-szymon.heidrich@gmail.com
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/net/wireless/rndis_wlan.c | 19 ++++++-------------
 1 file changed, 6 insertions(+), 13 deletions(-)

diff --git a/drivers/net/wireless/rndis_wlan.c b/drivers/net/wireless/rndis_wlan.c
index 82a7458e01ae..bf72e5fd39cf 100644
--- a/drivers/net/wireless/rndis_wlan.c
+++ b/drivers/net/wireless/rndis_wlan.c
@@ -696,8 +696,8 @@ static int rndis_query_oid(struct usbnet *dev, u32 oid, void *data, int *len)
 		struct rndis_query	*get;
 		struct rndis_query_c	*get_c;
 	} u;
-	int ret, buflen;
-	int resplen, respoffs, copylen;
+	int ret;
+	size_t buflen, resplen, respoffs, copylen;
 
 	buflen = *len + sizeof(*u.get);
 	if (buflen < CONTROL_BUFFER_SIZE)
@@ -732,22 +732,15 @@ static int rndis_query_oid(struct usbnet *dev, u32 oid, void *data, int *len)
 
 		if (respoffs > buflen) {
 			/* Device returned data offset outside buffer, error. */
-			netdev_dbg(dev->net, "%s(%s): received invalid "
-				"data offset: %d > %d\n", __func__,
-				oid_to_string(oid), respoffs, buflen);
+			netdev_dbg(dev->net,
+				   "%s(%s): received invalid data offset: %zu > %zu\n",
+				   __func__, oid_to_string(oid), respoffs, buflen);
 
 			ret = -EINVAL;
 			goto exit_unlock;
 		}
 
-		if ((resplen + respoffs) > buflen) {
-			/* Device would have returned more data if buffer would
-			 * have been big enough. Copy just the bits that we got.
-			 */
-			copylen = buflen - respoffs;
-		} else {
-			copylen = resplen;
-		}
+		copylen = min(resplen, buflen - respoffs);
 
 		if (copylen > *len)
 			copylen = *len;
-- 
2.35.3