linux-kernel - [RFC PATCH] usb: dwc3: ep0: Fix mem corruption on OUT transfers of more than 512 bytes

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Message-ID: <1433860550-25636-1-git-send-email-kishon@ti.com>
Date:	Tue, 9 Jun 2015 20:05:50 +0530
From:	Kishon Vijay Abraham I <kishon@...com>
To:	<balbi@...com>, <linux-usb@...r.kernel.org>,
	<linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:	<nsekhar@...com>, <kishon@...com>, <gregkh@...uxfoundation.org>
Subject: [RFC PATCH] usb: dwc3: ep0: Fix mem corruption on OUT transfers of more than 512 bytes

DWC3 uses bounce buffer to handle non max packet aligned OUT transfers and
the size of bounce buffer is 512 bytes. However if the host initiates OUT
transfers of size more than 512 bytes (and non max packet aligned), the
driver throws a WARN dump but still programs the TRB to receive more than
512 bytes. This will cause bounce buffer to overflow and corrupt the
adjacent memory locations which can be fatal.

Fix it by programming the TRB to receive a maximum of DWC3_EP0_BOUNCE_SIZE
(512) bytes.

Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
---
Steps to see the issue (before this patch)
1) Insert g_zero in DUT
2) run './testusb -t 14 -c 1 -s 520 -v 1' in host (size should be > 512)

The test should FAIL since bounce buffer can handle only 512 bytes, but the
test PASS. There is a WARN dump in DUT but still there will be memory
corruption since the bounce buffer overflows.

Tested this patch using USB3 Gen X CV (ch9 tests: usb2 and usb3, link layer
testing and MSC tests) and using USB2 X CV (ch9 tests, MSC tests).

After the patch, the tests timeout!
./testusb -t 14 -c 1 -s 514 -v 1
unknown speed	/dev/bus/usb/001/018	0
/dev/bus/usb/001/018 test 14 --> 110 (Connection timed out)

IMO a patch to fix this is required for stable releases too. So If this
patch is alright, I can post the patch cc'ing stable. While the actual fix
would be to have chained TRB, I'm not sure if it can go to stable
releases.
 drivers/usb/dwc3/ep0.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
index 2ef3c8d..8858c60 100644
--- a/drivers/usb/dwc3/ep0.c
+++ b/drivers/usb/dwc3/ep0.c
@@ -816,6 +816,11 @@ static void dwc3_ep0_complete_data(struct dwc3 *dwc,
 		unsigned maxp = ep0->endpoint.maxpacket;

 		transfer_size += (maxp - (transfer_size % maxp));
+
+		/* Maximum of DWC3_EP0_BOUNCE_SIZE can only be received */
+		if (transfer_size > DWC3_EP0_BOUNCE_SIZE)
+			transfer_size = DWC3_EP0_BOUNCE_SIZE;
+
 		transferred = min_t(u32, ur->length,
 				transfer_size - length);
 		memcpy(ur->buf, dwc->ep0_bounce, transferred);
@@ -937,11 +942,14 @@ static void __dwc3_ep0_do_control_data(struct dwc3 *dwc,
 			return;
 		}

-		WARN_ON(req->request.length > DWC3_EP0_BOUNCE_SIZE);
-
 		maxpacket = dep->endpoint.maxpacket;
 		transfer_size = roundup(req->request.length, maxpacket);

+		if (transfer_size > DWC3_EP0_BOUNCE_SIZE) {
+			dev_WARN(dwc->dev, "bounce buf can't handle req len\n");
+			transfer_size = DWC3_EP0_BOUNCE_SIZE;
+		}
+
 		dwc->ep0_bounced = true;

 		/*
-- 
1.7.9.5

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