Re: drivers/infiniband/hw/qedr/verbs.c:1925 qedr_create_user_qp() error: we previously assumed 'ctx' could be null (see line 1900)

From: Jason Gunthorpe
Date: Tue Feb 16 2021 - 14:04:39 EST

On Mon, Feb 15, 2021 at 04:31:25PM +0300, Dan Carpenter wrote:
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head: dcc0b49040c70ad827a7f3d58a21b01fdb14e749
> commit: 06e8d1df46ed52eca6915a2a76341ca65cc428b9 RDMA/qedr: Add support for user mode XRC-SRQ's
> config: x86_64-randconfig-m001-20210213 (attached as .config)
> compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
>
> smatch warnings:
> drivers/infiniband/hw/qedr/verbs.c:1925 qedr_create_user_qp() error: we previously assumed 'ctx' could be null (see line 1900)
>
> vim +/ctx +1925 drivers/infiniband/hw/qedr/verbs.c
>
> df15856132bc83 Amrani, Ram 2016-12-22 1830 static int qedr_create_user_qp(struct qedr_dev *dev,
> cecbcddf6461a1 Ram Amrani 2016-10-10 1831 struct qedr_qp *qp,
> df15856132bc83 Amrani, Ram 2016-12-22 1832 struct ib_pd *ibpd,
> df15856132bc83 Amrani, Ram 2016-12-22 1833 struct ib_udata *udata,
> df15856132bc83 Amrani, Ram 2016-12-22 1834 struct ib_qp_init_attr *attrs)
> cecbcddf6461a1 Ram Amrani 2016-10-10 1835 {
> df15856132bc83 Amrani, Ram 2016-12-22 1836 struct qed_rdma_create_qp_in_params in_params;
> df15856132bc83 Amrani, Ram 2016-12-22 1837 struct qed_rdma_create_qp_out_params out_params;
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1838 struct qedr_create_qp_uresp uresp = {};
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1839 struct qedr_create_qp_ureq ureq = {};
> 69ad0e7fe8452a Kalderon, Michal 2017-07-26 1840 int alloc_and_init = rdma_protocol_roce(&dev->ibdev, 1);
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1841 struct qedr_ucontext *ctx = NULL;
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1842 struct qedr_pd *pd = NULL;
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1843 int rc = 0;
> cecbcddf6461a1 Ram Amrani 2016-10-10 1844
> 82af6d19d8d922 Michal Kalderon 2019-10-27 1845 qp->create_type = QEDR_QP_CREATE_USER;
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1846
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1847 if (ibpd) {
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1848 pd = get_qedr_pd(ibpd);
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1849 ctx = pd->uctx;
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1850 }
>
> "ctx" is NULL on the else path.

Looks like ibpd can never be NULL, so this is dead code

> 06e8d1df46ed52 Yuval Basson 2020-07-22 1851
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1852 if (udata) {

udata also can never be null because this is called 'qedr_create_user_qp' ?

It is confusingly called with a xrcd test too, but xrcd's are only
currently possible if udata is set.

> 06e8d1df46ed52 Yuval Basson 2020-07-22 1853 rc = ib_copy_from_udata(&ureq, udata, min(sizeof(ureq),
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1854 udata->inlen));
> df15856132bc83 Amrani, Ram 2016-12-22 1855 if (rc) {
> df15856132bc83 Amrani, Ram 2016-12-22 1856 DP_ERR(dev, "Problem copying data from user space\n");
> df15856132bc83 Amrani, Ram 2016-12-22 1857 return rc;
> df15856132bc83 Amrani, Ram 2016-12-22 1858 }
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1859 }
> cecbcddf6461a1 Ram Amrani 2016-10-10 1860
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1861 if (qedr_qp_has_sq(qp)) {
> 72b894b09a96b7 Christoph Hellwig 2019-11-13 1862 /* SQ - read access only (0) */
> b0ea0fa5435f9d Jason Gunthorpe 2019-01-09 1863 rc = qedr_init_user_queue(udata, dev, &qp->usq, ureq.sq_addr,
> 72b894b09a96b7 Christoph Hellwig 2019-11-13 1864 ureq.sq_len, true, 0, alloc_and_init);
> df15856132bc83 Amrani, Ram 2016-12-22 1865 if (rc)
> df15856132bc83 Amrani, Ram 2016-12-22 1866 return rc;
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1867 }
> cecbcddf6461a1 Ram Amrani 2016-10-10 1868
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1869 if (qedr_qp_has_rq(qp)) {
> 72b894b09a96b7 Christoph Hellwig 2019-11-13 1870 /* RQ - read access only (0) */
> b0ea0fa5435f9d Jason Gunthorpe 2019-01-09 1871 rc = qedr_init_user_queue(udata, dev, &qp->urq, ureq.rq_addr,
> 72b894b09a96b7 Christoph Hellwig 2019-11-13 1872 ureq.rq_len, true, 0, alloc_and_init);
> df15856132bc83 Amrani, Ram 2016-12-22 1873 if (rc)
> df15856132bc83 Amrani, Ram 2016-12-22 1874 return rc;
> 40b173ddce0fc6 Yuval Bason 2018-08-09 1875 }
> df15856132bc83 Amrani, Ram 2016-12-22 1876
> df15856132bc83 Amrani, Ram 2016-12-22 1877 memset(&in_params, 0, sizeof(in_params));
> df15856132bc83 Amrani, Ram 2016-12-22 1878 qedr_init_common_qp_in_params(dev, pd, qp, attrs, false, &in_params);
> df15856132bc83 Amrani, Ram 2016-12-22 1879 in_params.qp_handle_lo = ureq.qp_handle_lo;
> df15856132bc83 Amrani, Ram 2016-12-22 1880 in_params.qp_handle_hi = ureq.qp_handle_hi;
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1881
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1882 if (qp->qp_type == IB_QPT_XRC_TGT) {
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1883 struct qedr_xrcd *xrcd = get_qedr_xrcd(attrs->xrcd);
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1884
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1885 in_params.xrcd_id = xrcd->xrcd_id;
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1886 in_params.qp_handle_lo = qp->qp_id;
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1887 in_params.use_srq = 1;
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1888 }
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1889
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1890 if (qedr_qp_has_sq(qp)) {
> df15856132bc83 Amrani, Ram 2016-12-22 1891 in_params.sq_num_pages = qp->usq.pbl_info.num_pbes;
> df15856132bc83 Amrani, Ram 2016-12-22 1892 in_params.sq_pbl_ptr = qp->usq.pbl_tbl->pa;
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1893 }
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1894
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1895 if (qedr_qp_has_rq(qp)) {
> df15856132bc83 Amrani, Ram 2016-12-22 1896 in_params.rq_num_pages = qp->urq.pbl_info.num_pbes;
> df15856132bc83 Amrani, Ram 2016-12-22 1897 in_params.rq_pbl_ptr = qp->urq.pbl_tbl->pa;
> 40b173ddce0fc6 Yuval Bason 2018-08-09 1898 }
> df15856132bc83 Amrani, Ram 2016-12-22 1899
> bbe4f4245271bd Michal Kalderon 2020-07-07 @1900 if (ctx)
> ^^^
> Check for NULL
>
> bbe4f4245271bd Michal Kalderon 2020-07-07 1901 SET_FIELD(in_params.flags, QED_ROCE_EDPM_MODE, ctx->edpm_mode);
> bbe4f4245271bd Michal Kalderon 2020-07-07 1902
> df15856132bc83 Amrani, Ram 2016-12-22 1903 qp->qed_qp = dev->ops->rdma_create_qp(dev->rdma_ctx,
> df15856132bc83 Amrani, Ram 2016-12-22 1904 &in_params, &out_params);
> df15856132bc83 Amrani, Ram 2016-12-22 1905
> df15856132bc83 Amrani, Ram 2016-12-22 1906 if (!qp->qed_qp) {
> df15856132bc83 Amrani, Ram 2016-12-22 1907 rc = -ENOMEM;
> df15856132bc83 Amrani, Ram 2016-12-22 1908 goto err1;
> df15856132bc83 Amrani, Ram 2016-12-22 1909 }
> df15856132bc83 Amrani, Ram 2016-12-22 1910
> 69ad0e7fe8452a Kalderon, Michal 2017-07-26 1911 if (rdma_protocol_iwarp(&dev->ibdev, 1))
> 69ad0e7fe8452a Kalderon, Michal 2017-07-26 1912 qedr_iwarp_populate_user_qp(dev, qp, &out_params);
> 69ad0e7fe8452a Kalderon, Michal 2017-07-26 1913
> df15856132bc83 Amrani, Ram 2016-12-22 1914 qp->qp_id = out_params.qp_id;
> df15856132bc83 Amrani, Ram 2016-12-22 1915 qp->icid = out_params.icid;
> df15856132bc83 Amrani, Ram 2016-12-22 1916
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1917 if (udata) {
> 97f612509294aa Michal Kalderon 2019-10-30 1918 rc = qedr_copy_qp_uresp(dev, qp, udata, &uresp);
> 97f612509294aa Michal Kalderon 2019-10-30 1919 if (rc)
> 97f612509294aa Michal Kalderon 2019-10-30 1920 goto err;
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1921 }
> 97f612509294aa Michal Kalderon 2019-10-30 1922
> 97f612509294aa Michal Kalderon 2019-10-30 1923 /* db offset was calculated in copy_qp_uresp, now set in the user q */
> 06e8d1df46ed52 Yuval Basson 2020-07-22 1924 if (qedr_qp_has_sq(qp)) {
> 97f612509294aa Michal Kalderon 2019-10-30 @1925 qp->usq.db_addr = ctx->dpi_addr + uresp.sq_db_offset;
> ^^^^^^^^^^^^^
> Can "ctx" be NULL here?

This would also not work right if udata == NULL

Whole function needs cleaning, but doesn't look buggy

Jason