IB/mthca: fix return value of error branch in mthca_init_cq()

We return 'err' in the error branch, but this variable may be set as zero
by the above code. Fix it by setting 'err' as a negative value before we
goto the error label.

Fixes: 74c2174e7b ("IB uverbs: add mthca user CQ support")
Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Link: https://lore.kernel.org/r/1605837422-42724-1-git-send-email-wangxiongfeng2@huawei.com
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/hw/mthca/mthca_cq.c

@@ -803,8 +803,10 @@ int mthca_init_cq(struct mthca_dev *dev, int nent,
 	}
 
 	mailbox = mthca_alloc_mailbox(dev, GFP_KERNEL);
-	if (IS_ERR(mailbox))
+	if (IS_ERR(mailbox)) {
+		err = PTR_ERR(mailbox);
 		goto err_out_arm;
+	}
 
 	cq_context = mailbox->buf;
 
@@ -846,9 +848,9 @@ int mthca_init_cq(struct mthca_dev *dev, int nent,
 	}
 
 	spin_lock_irq(&dev->cq_table.lock);
-	if (mthca_array_set(&dev->cq_table.cq,
-			    cq->cqn & (dev->limits.num_cqs - 1),
-			    cq)) {
+	err = mthca_array_set(&dev->cq_table.cq,
+			      cq->cqn & (dev->limits.num_cqs - 1), cq);
+	if (err) {
 		spin_unlock_irq(&dev->cq_table.lock);
 		goto err_out_free_mr;
 	}