linux-kernel - [PATCH] usbip: stub_rx: fix static checker warning on unnecessary checks

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Date:   Fri, 15 Dec 2017 10:05:15 -0700
From:   Shuah Khan <shuahkh@....samsung.com>
To:     valentina.manea.m@...il.com, shuah@...nel.org,
        gregkh@...uxfoundation.org
Cc:     Shuah Khan <shuahkh@....samsung.com>, dan.carpenter@...cle.com,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] usbip: stub_rx: fix static checker warning on unnecessary checks

Fix the following static checker warnings:

The patch c6688ef9f297: "usbip: fix stub_rx: harden CMD_SUBMIT path
to handle malicious input" from Dec 7, 2017, leads to the following
static checker warning:

    drivers/usb/usbip/stub_rx.c:346 get_pipe()
    warn: impossible condition
'(pdu->u.cmd_submit.transfer_buffer_length > ((~0 >> 1))) =>
(s32min-s32max > s32max)'
    drivers/usb/usbip/stub_rx.c:486 stub_recv_cmd_submit()
    warn: always true condition
'(pdu->u.cmd_submit.transfer_buffer_length <= ((~0 >> 1))) =>
(s32min-s32max <= s32max)'

Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Shuah Khan <shuahkh@....samsung.com>
---
 drivers/usb/usbip/stub_rx.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/drivers/usb/usbip/stub_rx.c b/drivers/usb/usbip/stub_rx.c
index 493ac2928391..b1820ab083e1 100644
--- a/drivers/usb/usbip/stub_rx.c
+++ b/drivers/usb/usbip/stub_rx.c
@@ -342,14 +342,6 @@ static int get_pipe(struct stub_device *sdev, struct usbip_header *pdu)
 
 	epd = &ep->desc;
 
-	/* validate transfer_buffer_length */
-	if (pdu->u.cmd_submit.transfer_buffer_length > INT_MAX) {
-		dev_err(&sdev->udev->dev,
-			"CMD_SUBMIT: -EMSGSIZE transfer_buffer_length %d\n",
-			pdu->u.cmd_submit.transfer_buffer_length);
-		return -1;
-	}
-
 	if (usb_endpoint_xfer_control(epd)) {
 		if (dir == USBIP_DIR_OUT)
 			return usb_sndctrlpipe(udev, epnum);
@@ -482,8 +474,7 @@ static void stub_recv_cmd_submit(struct stub_device *sdev,
 	}
 
 	/* allocate urb transfer buffer, if needed */
-	if (pdu->u.cmd_submit.transfer_buffer_length > 0 &&
-	    pdu->u.cmd_submit.transfer_buffer_length <= INT_MAX) {
+	if (pdu->u.cmd_submit.transfer_buffer_length > 0) {
 		priv->urb->transfer_buffer =
 			kzalloc(pdu->u.cmd_submit.transfer_buffer_length,
 				GFP_KERNEL);
-- 
2.14.1