patch "usbip: Fix uninitialized symbol 'nents' in stub_recv_cmd_submit()" added to usb-testing

patch "usbip: Fix uninitialized symbol 'nents' in stub_recv_cmd_submit()" added to usb-testing

[gregkh]

This is a note to let you know that I've just added the patch titled

    usbip: Fix uninitialized symbol 'nents' in stub_recv_cmd_submit()

to my usb git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-testing branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will be merged to the usb-next branch sometime soon,
after it passes testing, and the merge window is open.

If you have any questions about this process, please let me know.


From 2a9125317b247f2cf35c196f968906dcf062ae2d Mon Sep 17 00:00:00 2001
From: Suwan Kim <suwan.kim027@gmail.com>
Date: Mon, 11 Nov 2019 23:10:35 +0900
Subject: usbip: Fix uninitialized symbol 'nents' in stub_recv_cmd_submit()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Smatch reported that nents is not initialized and used in
stub_recv_cmd_submit(). nents is currently initialized by sgl_alloc()
and used to allocate multiple URBs when host controller doesn't
support scatter-gather DMA. The use of uninitialized nents means that
buf_len is zero and use_sg is true. But buffer length should not be
zero when an URB uses scatter-gather DMA.

To prevent this situation, add the conditional that checks buf_len
and use_sg. And move the use of nents right after the sgl_alloc() to
avoid the use of uninitialized nents.

If the error occurs, it adds SDEV_EVENT_ERROR_MALLOC and stub_priv
will be released by stub event handler and connection will be shut
down.

Fixes: ea44d190764b ("usbip: Implement SG support to vhci-hcd and stub driver")
Reported-by: kbuild test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Suwan Kim <suwan.kim027@gmail.com>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20191111141035.27788-1-suwan.kim027@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/usb/usbip/stub_rx.c | 50 ++++++++++++++++++++++++-------------
 1 file changed, 32 insertions(+), 18 deletions(-)

diff --git a/drivers/usb/usbip/stub_rx.c b/drivers/usb/usbip/stub_rx.c
index 66edfeea68fe..e2b019532234 100644
--- a/drivers/usb/usbip/stub_rx.c
+++ b/drivers/usb/usbip/stub_rx.c
@@ -470,18 +470,50 @@ static void stub_recv_cmd_submit(struct stub_device *sdev,
 	if (pipe == -1)
 		return;
 
+	/*
+	 * Smatch reported the error case where use_sg is true and buf_len is 0.
+	 * In this case, It adds SDEV_EVENT_ERROR_MALLOC and stub_priv will be
+	 * released by stub event handler and connection will be shut down.
+	 */
 	priv = stub_priv_alloc(sdev, pdu);
 	if (!priv)
 		return;
 
 	buf_len = (unsigned long long)pdu->u.cmd_submit.transfer_buffer_length;
 
+	if (use_sg && !buf_len) {
+		dev_err(&udev->dev, "sg buffer with zero length\n");
+		goto err_malloc;
+	}
+
 	/* allocate urb transfer buffer, if needed */
 	if (buf_len) {
 		if (use_sg) {
 			sgl = sgl_alloc(buf_len, GFP_KERNEL, &nents);
 			if (!sgl)
 				goto err_malloc;
+
+			/* Check if the server's HCD supports SG */
+			if (!udev->bus->sg_tablesize) {
+				/*
+				 * If the server's HCD doesn't support SG, break
+				 * a single SG request into several URBs and map
+				 * each SG list entry to corresponding URB
+				 * buffer. The previously allocated SG list is
+				 * stored in priv->sgl (If the server's HCD
+				 * support SG, SG list is stored only in
+				 * urb->sg) and it is used as an indicator that
+				 * the server split single SG request into
+				 * several URBs. Later, priv->sgl is used by
+				 * stub_complete() and stub_send_ret_submit() to
+				 * reassemble the divied URBs.
+				 */
+				support_sg = 0;
+				num_urbs = nents;
+				priv->completed_urbs = 0;
+				pdu->u.cmd_submit.transfer_flags &=
+								~URB_DMA_MAP_SG;
+			}
 		} else {
 			buffer = kzalloc(buf_len, GFP_KERNEL);
 			if (!buffer)
@@ -489,24 +521,6 @@ static void stub_recv_cmd_submit(struct stub_device *sdev,
 		}
 	}
 
-	/* Check if the server's HCD supports SG */
-	if (use_sg && !udev->bus->sg_tablesize) {
-		/*
-		 * If the server's HCD doesn't support SG, break a single SG
-		 * request into several URBs and map each SG list entry to
-		 * corresponding URB buffer. The previously allocated SG
-		 * list is stored in priv->sgl (If the server's HCD support SG,
-		 * SG list is stored only in urb->sg) and it is used as an
-		 * indicator that the server split single SG request into
-		 * several URBs. Later, priv->sgl is used by stub_complete() and
-		 * stub_send_ret_submit() to reassemble the divied URBs.
-		 */
-		support_sg = 0;
-		num_urbs = nents;
-		priv->completed_urbs = 0;
-		pdu->u.cmd_submit.transfer_flags &= ~URB_DMA_MAP_SG;
-	}
-
 	/* allocate urb array */
 	priv->num_urbs = num_urbs;
 	priv->urbs = kmalloc_array(num_urbs, sizeof(*priv->urbs), GFP_KERNEL);
-- 
2.24.0