RDMA/rxe: Always return ERR_PTR from rxe_create_mmap_info()

The commit below modified rxe_create_mmap_info() to return ERR_PTR's but
didn't update the callers to handle them. Modify rxe_create_mmap_info() to
only return ERR_PTR and fix all error checking after
rxe_create_mmap_info() is called.

Ensure that all other exit paths properly set the error return.

Fixes: ff23dfa ("IB: Pass only ib_udata in function prototypes")
Link: https://lore.kernel.org/r/20200425233545.17210-1-sudipm.mukherjee@gmail.com
Link: https://lore.kernel.org/r/20200511183742.GB225608@mwanda
Cc: stable@vger.kernel.org [5.4+]
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/sw/rxe/rxe_mmap.c

@@ -151,7 +151,7 @@ struct rxe_mmap_info *rxe_create_mmap_info(struct rxe_dev *rxe, u32 size,
 
 	ip = kmalloc(sizeof(*ip), GFP_KERNEL);
 	if (!ip)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	size = PAGE_ALIGN(size);
 

drivers/infiniband/sw/rxe/rxe_queue.c

@@ -45,12 +45,15 @@ int do_mmap_info(struct rxe_dev *rxe, struct mminfo __user *outbuf,
 
 	if (outbuf) {
 		ip = rxe_create_mmap_info(rxe, buf_size, udata, buf);
-		if (!ip)
+		if (IS_ERR(ip)) {
+			err = PTR_ERR(ip);
 			goto err1;
+		}
 
-		err = copy_to_user(outbuf, &ip->info, sizeof(ip->info));
-		if (err)
+		if (copy_to_user(outbuf, &ip->info, sizeof(ip->info))) {
+			err = -EFAULT;
 			goto err2;
+		}
 
 		spin_lock_bh(&rxe->pending_lock);
 		list_add(&ip->pending_mmaps, &rxe->pending_mmaps);
@@ -64,7 +67,7 @@ int do_mmap_info(struct rxe_dev *rxe, struct mminfo __user *outbuf,
 err2:
 	kfree(ip);
 err1:
-	return -EINVAL;
+	return err;
 }
 
 inline void rxe_queue_reset(struct rxe_queue *q)