The following modify sequence (loosely based on ipoib) will lose a pkey
modifcation:

- Modify (pkey index, port)
- Modify (new pkey index, NO port)

After the first modify, the qp_pps list will have saved the pkey and the
unit on the main list.

During the second modify, get_new_pps() will fetch the port from qp_pps
and read the new pkey index from qp_attr->pkey_index.  The state will
still be zero, or IB_PORT_PKEY_NOT_VALID. Because of the invalid state,
the new values will never replace the one in the qp pps list, losing the
new pkey.

This happens because the following if statements will never correct the
state because the first term will be false. If the code had been executed,
it would incorrectly overwrite valid values.

  if ((qp_attr_mask & IB_QP_PKEY_INDEX) && (qp_attr_mask & IB_QP_PORT))
	  new_pps->main.state = IB_PORT_PKEY_VALID;

  if (!(qp_attr_mask & (IB_QP_PKEY_INDEX | IB_QP_PORT)) && qp_pps) {
	  new_pps->main.port_num = qp_pps->main.port_num;
	  new_pps->main.pkey_index = qp_pps->main.pkey_index;
	  if (qp_pps->main.state != IB_PORT_PKEY_NOT_VALID)
		  new_pps->main.state = IB_PORT_PKEY_VALID;
  }

Fix by joining the two if statements with an or test to see if qp_pps is
non-NULL and in the correct state.

Fixes: 1dd01788 ("RDMA/core: Fix protection fault in get_pkey_idx_qp_list")
Link: https://lore.kernel.org/r/20200313124704.14982.55907.stgit@awfm-01.aw.intel.comReviewed-by: Kaike Wan <kaike.wan@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>