Commit 48973c6c authored by Jason Gunthorpe's avatar Jason Gunthorpe
Browse files

RDMA/hns: Fix xarray race in hns_roce_create_srq() 

Sashiko points out that once the srq memory is stored into the xarray by
alloc_srqc() it can immediately be looked up by:

	xa_lock(&srq_table->xa);
	srq = xa_load(&srq_table->xa, srqn & (hr_dev->caps.num_srqs - 1));
	if (srq)
		refcount_inc(&srq->refcount);
	xa_unlock(&srq_table->xa);

Which will fail refcount debug because the refcount is 0 and then crash:

	srq->event(srq, event_type);

Because event is NULL.

Use refcount_inc_not_zero() instead to ensure a partially prepared srq is
never retrieved from the event handler and fix the ordering of the
initialization so refcount becomes 1 only after it is fully ready.

All the initialization must be done before calling free_srqc() since it
depends on the completion and refcount.

Fixes: 9a443537 ("IB/hns: Add driver files for hns RoCE driver")
Link: https://sashiko.dev/#/patchset/0-v1-e911b76a94d1%2B65d95-rdma_udata_rep_jgg%40nvidia.com?part=3
Link: https://patch.msgid.link/r/13-v1-41f3135e5565+9d2-rdma_ai_fixes1_jgg@nvidia.com


Reviewed-by: default avatarJunxian Huang <huangjunxian6@hisilicon.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@nvidia.com>
parent c9341307

drivers/infiniband/hw/hns/hns_roce_srq.c

+6 −6
Original line number Diff line number Diff line
@@ -16,8 +16,8 @@ void hns_roce_srq_event(struct hns_roce_dev *hr_dev, u32 srqn, int event_type) 


	xa_lock(&srq_table->xa);

	srq = xa_load(&srq_table->xa, srqn & (hr_dev->caps.num_srqs - 1));

	if (srq)

		refcount_inc(&srq->refcount);

	if (srq && !refcount_inc_not_zero(&srq->refcount))

		srq = NULL;

	xa_unlock(&srq_table->xa);



	if (!srq) {
@@ -470,6 +470,10 @@ int hns_roce_create_srq(struct ib_srq *ib_srq, 
	if (ret)

		goto err_srqn;



	srq->event = hns_roce_ib_srq_event;

	init_completion(&srq->free);

	refcount_set_release(&srq->refcount, 1);



	if (udata) {

		resp.cap_flags = srq->cap_flags;

		resp.srqn = srq->srqn;
@@ -480,10 +484,6 @@ int hns_roce_create_srq(struct ib_srq *ib_srq, 
		}

	}



	srq->event = hns_roce_ib_srq_event;

	refcount_set(&srq->refcount, 1);

	init_completion(&srq->free);



	return 0;



err_srqc: