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Date:   Wed, 23 Oct 2019 16:11:20 +0900
From:   Suwan Kim <suwan.kim027@gmail.com>
To:     Dan Carpenter <dan.carpenter@oracle.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@kernel.org
Subject: Re: drivers/usb/usbip/stub_rx.c:505 stub_recv_cmd_submit() error:
 uninitialized symbol 'nents'.
Message-ID: <20191023071120.GA3061@localhost.localdomain>
References: <20191022092839.GD10833@kadam>
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In-Reply-To: <20191022092839.GD10833@kadam>
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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? If then, Did Smatch also
consider vhci tx side?

Regards
Suwan Kim

> ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  494  		/*
> ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  495  		 * If the server's HCD doesn't support SG, break a single SG
> ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  496  		 * request into several URBs and map each SG list entry to
> ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  497  		 * corresponding URB buffer. The previously allocated SG
> ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  498  		 * list is stored in priv->sgl (If the server's HCD support SG,
> ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  499  		 * SG list is stored only in urb->sg) and it is used as an
> ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  500  		 * indicator that the server split single SG request into
> ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  501  		 * several URBs. Later, priv->sgl is used by stub_complete() and
> ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  502  		 * stub_send_ret_submit() to reassemble the divied URBs.
> ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  503  		 */
> ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  504  		support_sg = 0;
> ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28 @505  		num_urbs = nents;
>                                                                                                 ^^^^^^^^^^^^^^^^
> 
> ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  506  		priv->completed_urbs = 0;
> ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  507  		pdu->u.cmd_submit.transfer_flags &= ~URB_DMA_MAP_SG;
> ea44d190764b44 drivers/usb/usbip/stub_rx.c     Suwan Kim          2019-08-28  508  	}
> 
> ---
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