linux-kernel - [PATCH 3/8] usb: gadget: f_acm: validate set_line

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Message-Id: <1497288375-3559-4-git-send-email-tal.shorer@gmail.com>
Date:   Mon, 12 Jun 2017 20:26:10 +0300
From:   Tal Shorer <tal.shorer@...il.com>
To:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org, gregkh@...uxfoundation.org,
        balbi@...nel.org, corbet@....net
Cc:     Tal Shorer <tal.shorer@...il.com>
Subject: [PATCH 3/8] usb: gadget: f_acm: validate set_line_coding requests

We shouldn't accept malformed set_line_coding requests.
All values were taken from table 17 (section 6.3.11) of the cdc1.2 spec
available at http://www.usb.org/developers/docs/devclass_docs/
The table is in the file PTSN120.pdf.

Signed-off-by: Tal Shorer <tal.shorer@...il.com>
---
 drivers/usb/gadget/function/f_acm.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/drivers/usb/gadget/function/f_acm.c b/drivers/usb/gadget/function/f_acm.c
index 5e3828d..e023313 100644
--- a/drivers/usb/gadget/function/f_acm.c
+++ b/drivers/usb/gadget/function/f_acm.c
@@ -326,13 +326,22 @@ static void acm_complete_set_line_coding(struct usb_ep *ep,
 		struct usb_cdc_line_coding	*value = req->buf;
 
 		/* REVISIT:  we currently just remember this data.
-		 * If we change that, (a) validate it first, then
-		 * (b) update whatever hardware needs updating,
-		 * (c) worry about locking.  This is information on
-		 * the order of 9600-8-N-1 ... most of which means
-		 * nothing unless we control a real RS232 line.
-		 */
-		acm->port_line_coding = *value;
+		* If we change that,
+		* (a) update whatever hardware needs updating,
+		* (b) worry about locking.  This is information on
+		* the order of 9600-8-N-1 ... most of which means
+		* nothing unless we control a real RS232 line.
+		*/
+		dev_dbg(&cdev->gadget->dev,
+			"acm ttyGS%d set_line_coding: %d %d %d %d\n",
+			acm->port_num, le32_to_cpu(value->dwDTERate),
+			value->bCharFormat, value->bParityType,
+			value->bDataBits);
+		if (value->bCharFormat > 2 || value->bParityType > 4 ||
+				value->bDataBits < 5 || value->bDataBits > 8)
+			usb_ep_set_halt(ep);
+		else
+			acm->port_line_coding = *value;
 	}
 }
 
-- 
2.7.4