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From:   Jim Lin <jilin@nvidia.com>
To:     <balbi@kernel.org>, <gregkh@linuxfoundation.org>
CC:     <linux-usb@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        Jim Lin <jilin@nvidia.com>,
        Aniruddha TVS Rao <anrao@nvidia.com>
Subject: [PATCH] usb: gadget: rndis: Avoid dereference before NULL check
Date:   Fri, 9 Sep 2022 01:56:15 +0800
Message-ID: <20220908175615.5095-1-jilin@nvidia.com>
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NULL check is performed after params->dev is dereferenced in
dev_get_stats.
Fixed by adding a NULL check before dereferencing params->dev and
removing subsequent NULL checks for it.

Signed-off-by: Aniruddha TVS Rao <anrao@nvidia.com>
Signed-off-by: Jim Lin <jilin@nvidia.com>
---
 drivers/usb/gadget/function/rndis.c | 37 ++++++++++++-----------------
 1 file changed, 15 insertions(+), 22 deletions(-)

diff --git a/drivers/usb/gadget/function/rndis.c b/drivers/usb/gadget/function/rndis.c
index 64de9f1b874c..d2f18f34c8e5 100644
--- a/drivers/usb/gadget/function/rndis.c
+++ b/drivers/usb/gadget/function/rndis.c
@@ -198,6 +198,9 @@ static int gen_ndis_query_resp(struct rndis_params *params, u32 OID, u8 *buf,
 	outbuf = (__le32 *)&resp[1];
 	resp->InformationBufferOffset = cpu_to_le32(16);
 
+	if (!params->dev)
+		return -ENODEV;
+
 	net = params->dev;
 	stats = dev_get_stats(net, &temp);
 
@@ -246,10 +249,8 @@ static int gen_ndis_query_resp(struct rndis_params *params, u32 OID, u8 *buf,
 	/* mandatory */
 	case RNDIS_OID_GEN_MAXIMUM_FRAME_SIZE:
 		pr_debug("%s: RNDIS_OID_GEN_MAXIMUM_FRAME_SIZE\n", __func__);
-		if (params->dev) {
-			*outbuf = cpu_to_le32(params->dev->mtu);
-			retval = 0;
-		}
+		*outbuf = cpu_to_le32(params->dev->mtu);
+		retval = 0;
 		break;
 
 	/* mandatory */
@@ -266,19 +267,15 @@ static int gen_ndis_query_resp(struct rndis_params *params, u32 OID, u8 *buf,
 	/* mandatory */
 	case RNDIS_OID_GEN_TRANSMIT_BLOCK_SIZE:
 		pr_debug("%s: RNDIS_OID_GEN_TRANSMIT_BLOCK_SIZE\n", __func__);
-		if (params->dev) {
-			*outbuf = cpu_to_le32(params->dev->mtu);
-			retval = 0;
-		}
+		*outbuf = cpu_to_le32(params->dev->mtu);
+		retval = 0;
 		break;
 
 	/* mandatory */
 	case RNDIS_OID_GEN_RECEIVE_BLOCK_SIZE:
 		pr_debug("%s: RNDIS_OID_GEN_RECEIVE_BLOCK_SIZE\n", __func__);
-		if (params->dev) {
-			*outbuf = cpu_to_le32(params->dev->mtu);
-			retval = 0;
-		}
+		*outbuf = cpu_to_le32(params->dev->mtu);
+		retval = 0;
 		break;
 
 	/* mandatory */
@@ -405,21 +402,17 @@ static int gen_ndis_query_resp(struct rndis_params *params, u32 OID, u8 *buf,
 	/* mandatory */
 	case RNDIS_OID_802_3_PERMANENT_ADDRESS:
 		pr_debug("%s: RNDIS_OID_802_3_PERMANENT_ADDRESS\n", __func__);
-		if (params->dev) {
-			length = ETH_ALEN;
-			memcpy(outbuf, params->host_mac, length);
-			retval = 0;
-		}
+		length = ETH_ALEN;
+		memcpy(outbuf, params->host_mac, length);
+		retval = 0;
 		break;
 
 	/* mandatory */
 	case RNDIS_OID_802_3_CURRENT_ADDRESS:
 		pr_debug("%s: RNDIS_OID_802_3_CURRENT_ADDRESS\n", __func__);
-		if (params->dev) {
-			length = ETH_ALEN;
-			memcpy(outbuf, params->host_mac, length);
-			retval = 0;
-		}
+		length = ETH_ALEN;
+		memcpy(outbuf, params->host_mac, length);
+		retval = 0;
 		break;
 
 	/* mandatory */
-- 
2.17.1