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

From: Suwan Kim
Date: Fri Oct 25 2019 - 23:40:31 EST

On Thu, Oct 24, 2019 at 04:52:52PM -0600, shuah wrote:
> 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.

Or Is it your intention to check as follows?
I think this looks good.

...
int nents = 0

...

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

/* Additional check here */
if (use_sg && !nents) {
err_message;
goto err_urbs;
}

/* Check if the server's HCD supports SG */
if (use_sg && !udev->bus->sg_tablesize) {

Regards,
Suwan Kim