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Subject: Re: drivers/usb/usbip/stub_rx.c:505 stub_recv_cmd_submit() error:
 uninitialized symbol 'nents'.
To:     Dan Carpenter <dan.carpenter@oracle.com>,
        Suwan Kim <suwan.kim027@gmail.com>
Cc:     kbuild@lists.01.org, kbuild-all@lists.01.org,
        linux-kernel@vger.kernel.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-usb@vger.kernel.org, shuah <shuah@kernel.org>
References: <20191022092839.GD10833@kadam>
 <20191023071120.GA3061@localhost.localdomain> <20191024194500.GD23523@kadam>
From:   shuah <shuah@kernel.org>
Message-ID: <ce76c90b-3431-9342-8b75-882d582c6366@kernel.org>
Date:   Thu, 24 Oct 2019 16:52:52 -0600
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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@intel.com>
>>> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
>>>
>>> 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