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Date: Tue, 29 Oct 2019 05:07:58 -0600
From: shuah <shuah@...nel.org>
To: Suwan Kim <suwan.kim027@...il.com>
Cc: Dan Carpenter <dan.carpenter@...cle.com>, kbuild@...ts.01.org,
kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
linux-usb@...r.kernel.org, shuah <shuah@...nel.org>
Subject: Re: drivers/usb/usbip/stub_rx.c:505 stub_recv_cmd_submit() error:
uninitialized symbol 'nents'.
On 10/25/19 9:40 PM, Suwan Kim wrote:
> 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@...el.com>
>>>>> Reported-by: Dan Carpenter <dan.carpenter@...cle.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.
>
> 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;
Why can't we move the
> /* Check if the server's HCD supports SG */
> if (use_sg && !udev->bus->sg_tablesize) {
>
under this check?
> } 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) {
>
thanks,
-- Shuah
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