RDMA/core: Fix unsafe linked list traversal after failing to allocate CQ

It's not safe to access the next CQ in list_for_each_entry() after
invoking ib_free_cq(), because the CQ has already been freed in current
iteration.  It should be replaced by list_for_each_entry_safe().

Fixes: c7ff819a ("RDMA/core: Introduce shared CQ pool API")
Link: https://lore.kernel.org/r/1598963935-32335-1-git-send-email-liweihang@huawei.comSigned-off-by: Xi Wang <wangxi11@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/core/cq.c

@@ -379,7 +379,7 @@ static int ib_alloc_cqs(struct ib_device *dev, unsigned int nr_cqes,
 {
 	LIST_HEAD(tmp_list);
 	unsigned int nr_cqs, i;
-	struct ib_cq *cq;
+	struct ib_cq *cq, *n;
 	int ret;
 
 	if (poll_ctx > IB_POLL_LAST_POOL_TYPE) {
@@ -412,7 +412,7 @@ static int ib_alloc_cqs(struct ib_device *dev, unsigned int nr_cqes,
 	return 0;
 
 out_free_cqs:
-	list_for_each_entry(cq, &tmp_list, pool_entry) {
+	list_for_each_entry_safe(cq, n, &tmp_list, pool_entry) {
 		cq->shared = false;
 		ib_free_cq(cq);
 	}