Re: drivers/usb/usbip/stub_rx.c:505 stub_recv_cmd_submit() error: uninitialized symbol 'nents'.

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On 10/24/19 1:45 PM, Dan Carpenter wrote:
On Wed, Oct 23, 2019 at 04:11:20PM +0900, Suwan Kim wrote:
On Tue, Oct 22, 2019 at 12:28:39PM +0300, Dan Carpenter wrote:
tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   7d194c2100ad2a6dded545887d02754948ca5241
commit: ea44d190764b4422af4d1c29eaeb9e69e353b406 usbip: Implement SG support to vhci-hcd and stub driver
date:   7 weeks ago

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@xxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

New smatch warnings:
drivers/usb/usbip/stub_rx.c:505 stub_recv_cmd_submit() error: uninitialized symbol 'nents'.

Old smatch warnings:
drivers/usb/usbip/stub_rx.c:450 stub_recv_xbuff() error: uninitialized symbol 'ret'.

# https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ea44d190764b4422af4d1c29eaeb9e69e353b406
git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
git remote update linus
git checkout ea44d190764b4422af4d1c29eaeb9e69e353b406
vim +/nents +505 drivers/usb/usbip/stub_rx.c

4d7b5c7f8ad49b drivers/staging/usbip/stub_rx.c Takahiro Hirofuchi 2008-07-09  453  static void stub_recv_cmd_submit(struct stub_device *sdev,
4d7b5c7f8ad49b drivers/staging/usbip/stub_rx.c Takahiro Hirofuchi 2008-07-09  454  				 struct usbip_header *pdu)
4d7b5c7f8ad49b drivers/staging/usbip/stub_rx.c Takahiro Hirofuchi 2008-07-09  455  {
4d7b5c7f8ad49b drivers/staging/usbip/stub_rx.c Takahiro Hirofuchi 2008-07-09  456  	struct stub_priv *priv;
4d7b5c7f8ad49b drivers/staging/usbip/stub_rx.c Takahiro Hirofuchi 2008-07-09  457  	struct usbip_device *ud = &sdev->ud;
2d8f4595d1f275 drivers/staging/usbip/stub_rx.c Max Vozeler        2011-01-12  458  	struct usb_device *udev = sdev->udev;
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  459  	struct scatterlist *sgl = NULL, *sg;
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  460  	void *buffer = NULL;
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  461  	unsigned long long buf_len;
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  462  	int nents;
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  463  	int num_urbs = 1;
c6688ef9f29762 drivers/usb/usbip/stub_rx.c     Shuah Khan         2017-12-07  464  	int pipe = get_pipe(sdev, pdu);
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  465  	int use_sg = pdu->u.cmd_submit.transfer_flags & URB_DMA_MAP_SG;
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  466  	int support_sg = 1;
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  467  	int np = 0;
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  468  	int ret, i;
4d7b5c7f8ad49b drivers/staging/usbip/stub_rx.c Takahiro Hirofuchi 2008-07-09  469
635f545a7e8be7 drivers/usb/usbip/stub_rx.c     Shuah Khan         2017-12-07  470  	if (pipe == -1)
635f545a7e8be7 drivers/usb/usbip/stub_rx.c     Shuah Khan         2017-12-07  471  		return;
4d7b5c7f8ad49b drivers/staging/usbip/stub_rx.c Takahiro Hirofuchi 2008-07-09  472
4d7b5c7f8ad49b drivers/staging/usbip/stub_rx.c Takahiro Hirofuchi 2008-07-09  473  	priv = stub_priv_alloc(sdev, pdu);
4d7b5c7f8ad49b drivers/staging/usbip/stub_rx.c Takahiro Hirofuchi 2008-07-09  474  	if (!priv)
4d7b5c7f8ad49b drivers/staging/usbip/stub_rx.c Takahiro Hirofuchi 2008-07-09  475  		return;
4d7b5c7f8ad49b drivers/staging/usbip/stub_rx.c Takahiro Hirofuchi 2008-07-09  476
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  477  	buf_len = (unsigned long long)pdu->u.cmd_submit.transfer_buffer_length;
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  478
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  479  	/* allocate urb transfer buffer, if needed */
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  480  	if (buf_len) {
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  481  		if (use_sg) {
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  482  			sgl = sgl_alloc(buf_len, GFP_KERNEL, &nents);
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  483  			if (!sgl)
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  484  				goto err_malloc;
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  485  		} else {
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  486  			buffer = kzalloc(buf_len, GFP_KERNEL);
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  487  			if (!buffer)
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  488  				goto err_malloc;
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  489  		}
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  490  	}
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  491
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  492  	/* Check if the server's HCD supports SG */
ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  493  	if (use_sg && !udev->bus->sg_tablesize) {

Smatch thinks "use_sg" can be true when "buf_len" is zero.  It's hard
to tell if Smatch is right or wrong without more context...

This is a bit strange. The meaning of "use_sg" is that client will
use scatter-gather and client's urb->num_sgs is not zero. And buffer
length should not be zero.

usb_sg and buf_len are both client-dependent variables, so I think
if they have wrong value in the server side, the client must have
sent use_sg and buf_len with incorrect values.

Did this error occur when compiling?

Smatch is doing static analysis, yes.

If then, Did Smatch also consider vhci tx side?

I'm not really sure...  I can't reproduce the warning because on my
system Smatch doesn't parse usbip_recv() correctly so it ends up
silencing that warning.  :/


Hi Suwan,

This is a problem that needs fixing. nents

       /* allocate urb transfer buffer, if needed */
        if (buf_len) {
                if (use_sg) {
                        sgl = sgl_alloc(buf_len, GFP_KERNEL, &nents);

nents gets initialized here by sgl_alloc()

                        if (!sgl)
                                goto err_malloc;
                } else {
                        buffer = kzalloc(buf_len, GFP_KERNEL);
                        if (!buffer)
                                goto err_malloc;
                }
        }

        /* 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;

I think nents will be valid here. Is there need for this additional
check here? You can fold this into the previous use_sg check, right
after the sg_alloc() success, I would think.

                priv->completed_urbs = 0;
                pdu->u.cmd_submit.transfer_flags &= ~URB_DMA_MAP_SG;
        }


thanks,
-- Shuah




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