IB/mlx5: Add missing error code

stable inclusion
from stable-5.10.22
commit 7ef9d23bc3121be3e77ed7fbcf9d3c9ecbf7005e
bugzilla: 50796

--------------------------------

[ Upstream commit 3a9b3d45 ]

Set err to -ENOMEM if kzalloc fails instead of 0.

Fixes: 75973853 ("IB/mlx5: Enable subscription for device events over DEVX")
Link: https://lore.kernel.org/r/20210222122343.19720-1-yuehaibing@huawei.comSigned-off-by: NYueHaibing <yuehaibing@huawei.com>
Acked-by: NLeon Romanovsky <leonro@nvidia.com>
Signed-off-by: NJason Gunthorpe <jgg@nvidia.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: N  Weilong Chen <chenweilong@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/infiniband/hw/mlx5/devx.c

@@ -1973,8 +1973,10 @@ static int UVERBS_HANDLER(MLX5_IB_METHOD_DEVX_SUBSCRIBE_EVENT)(
 
 		num_alloc_xa_entries++;
 		event_sub = kzalloc(sizeof(*event_sub), GFP_KERNEL);
-		if (!event_sub)
+		if (!event_sub) {
+			err = -ENOMEM;
 			goto err;
+		}
 
 		list_add_tail(&event_sub->event_list, &sub_list);
 		uverbs_uobject_get(&ev_file->uobj);