RDMA/mlx5: Handle DCT QP logic separately from low level QP interface

Previously when destroying a DCT, if the firmware function for the
destruction failed, the common resource would have been destroyed
either way, since it was destroyed before the firmware object.
Which leads to kernel warning "refcount_t: underflow" which indicates
possible use-after-free.
Which is triggered when we try to destroy the common resource for the
second time and execute refcount_dec_and_test(&common->refcount).

So, let's fix the destruction order by factoring out the DCT QP logic
to be in separate XArray database.

refcount_t: underflow; use-after-free.
WARNING: CPU: 8 PID: 1002 at lib/refcount.c:28 refcount_warn_saturate+0xd8/0xe0
Modules linked in: xt_conntrack xt_MASQUERADE nf_conntrack_netlink nfnetlink xt_addrtype iptable_nat nf_nat br_netfilter rpcrdma rdma_ucm ib_iser libiscsi scsi_transport_iscsi ib_umad rdma_cm ib_ipoib iw_cm ib_cm mlx5_ib ib_uverbs ib_core overlay mlx5_core fuse
CPU: 8 PID: 1002 Comm: python3 Not tainted 5.16.0-rc5+ #1
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
RIP: 0010:refcount_warn_saturate+0xd8/0xe0
Code: ff 48 c7 c7 18 f5 23 82 c6 05 60 70 ff 00 01 e8 d0 0a 45 00 0f 0b c3 48 c7 c7 c0 f4 23 82 c6 05 4c 70 ff 00 01 e8 ba 0a 45 00 <0f> 0b c3 0f 1f 44 00 00 8b 07 3d 00 00 00 c0 74 12 83 f8 01 74 13
RSP: 0018:ffff8881221d3aa8 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffff8881313e8d40 RCX: ffff88852cc1b5c8
RDX: 00000000ffffffd8 RSI: 0000000000000027 RDI: ffff88852cc1b5c0
RBP: ffff888100f70000 R08: ffff88853ffd1ba8 R09: 0000000000000003
R10: 00000000fffff000 R11: 3fffffffffffffff R12: 0000000000000246
R13: ffff888100f71fa0 R14: ffff8881221d3c68 R15: 0000000000000020
FS:  00007efebbb13740(0000) GS:ffff88852cc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005611aac29f80 CR3: 00000001313de004 CR4: 0000000000370ea0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 destroy_resource_common+0x6e/0x95 [mlx5_ib]
 mlx5_core_destroy_rq_tracked+0x38/0xbe [mlx5_ib]
 mlx5_ib_destroy_wq+0x22/0x80 [mlx5_ib]
 ib_destroy_wq_user+0x1f/0x40 [ib_core]
 uverbs_free_wq+0x19/0x40 [ib_uverbs]
 destroy_hw_idr_uobject+0x18/0x50 [ib_uverbs]
 uverbs_destroy_uobject+0x2f/0x190 [ib_uverbs]
 uobj_destroy+0x3c/0x80 [ib_uverbs]
 ib_uverbs_cmd_verbs+0x3e4/0xb80 [ib_uverbs]
 ? uverbs_free_wq+0x40/0x40 [ib_uverbs]
 ? ip_list_rcv+0xf7/0x120
 ? netif_receive_skb_list_internal+0x1b6/0x2d0
 ? task_tick_fair+0xbf/0x450
 ? __handle_mm_fault+0x11fc/0x1450
 ib_uverbs_ioctl+0xa4/0x110 [ib_uverbs]
 __x64_sys_ioctl+0x3e4/0x8e0
 ? handle_mm_fault+0xb9/0x210
 do_syscall_64+0x3d/0x90
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7efebc0be17b
Code: 0f 1e fa 48 8b 05 1d ad 0c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d ed ac 0c 00 f7 d8 64 89 01 48
RSP: 002b:00007ffe71813e78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ffe71813fb8 RCX: 00007efebc0be17b
RDX: 00007ffe71813fa0 RSI: 00000000c0181b01 RDI: 0000000000000005
RBP: 00007ffe71813f80 R08: 00005611aae96020 R09: 000000000000004f
R10: 00007efebbf9ffa0 R11: 0000000000000246 R12: 00007ffe71813f80
R13: 00007ffe71813f4c R14: 00005611aae2eca0 R15: 00007efeae6c89d0
 </TASK>
Signed-off-by: Patrisious Haddad <phaddad@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/4470888466c8a898edc9833286967529cc5f3c0d.1685953497.git.leon@kernel.orgSigned-off-by: Leon Romanovsky <leon@kernel.org>

drivers/infiniband/hw/mlx5/qp.h

@@ -10,6 +10,7 @@ struct mlx5_ib_dev;
 
 struct mlx5_qp_table {
 	struct notifier_block nb;
+	struct xarray dct_xa;
 
 	/* protect radix tree
 	 */

drivers/infiniband/hw/mlx5/qpc.c

@@ -88,23 +88,35 @@ static bool is_event_type_allowed(int rsc_type, int event_type)
 	}
 }
 
+static int dct_event_notifier(struct mlx5_ib_dev *dev, struct mlx5_eqe *eqe)
+{
+	struct mlx5_core_dct *dct;
+	unsigned long flags;
+	u32 qpn;
+
+	qpn = be32_to_cpu(eqe->data.dct.dctn) & 0xFFFFFF;
+	xa_lock_irqsave(&dev->qp_table.dct_xa, flags);
+	dct = xa_load(&dev->qp_table.dct_xa, qpn);
+	if (dct)
+		complete(&dct->drained);
+	xa_unlock_irqrestore(&dev->qp_table.dct_xa, flags);
+	return NOTIFY_OK;
+}
+
 static int rsc_event_notifier(struct notifier_block *nb,
 			      unsigned long type, void *data)
 {
+	struct mlx5_ib_dev *dev =
+		container_of(nb, struct mlx5_ib_dev, qp_table.nb);
 	struct mlx5_core_rsc_common *common;
-	struct mlx5_qp_table *table;
-	struct mlx5_core_dct *dct;
+	struct mlx5_eqe *eqe = data;
 	u8 event_type = (u8)type;
 	struct mlx5_core_qp *qp;
-	struct mlx5_eqe *eqe;
 	u32 rsn;
 
 	switch (event_type) {
 	case MLX5_EVENT_TYPE_DCT_DRAINED:
-		eqe = data;
-		rsn = be32_to_cpu(eqe->data.dct.dctn) & 0xffffff;
-		rsn |= (MLX5_RES_DCT << MLX5_USER_INDEX_LEN);
-		break;
+		return dct_event_notifier(dev, eqe);
 	case MLX5_EVENT_TYPE_PATH_MIG:
 	case MLX5_EVENT_TYPE_COMM_EST:
 	case MLX5_EVENT_TYPE_SQ_DRAINED:
@@ -113,7 +125,6 @@ static int rsc_event_notifier(struct notifier_block *nb,
 	case MLX5_EVENT_TYPE_PATH_MIG_FAILED:
 	case MLX5_EVENT_TYPE_WQ_INVAL_REQ_ERROR:
 	case MLX5_EVENT_TYPE_WQ_ACCESS_ERROR:
-		eqe = data;
 		rsn = be32_to_cpu(eqe->data.qp_srq.qp_srq_n) & 0xffffff;
 		rsn |= (eqe->data.qp_srq.type << MLX5_USER_INDEX_LEN);
 		break;
@@ -121,8 +132,7 @@ static int rsc_event_notifier(struct notifier_block *nb,
 		return NOTIFY_DONE;
 	}
 
-	table = container_of(nb, struct mlx5_qp_table, nb);
-	common = mlx5_get_rsc(table, rsn);
+	common = mlx5_get_rsc(&dev->qp_table, rsn);
 	if (!common)
 		return NOTIFY_OK;
 
@@ -137,11 +147,6 @@ static int rsc_event_notifier(struct notifier_block *nb,
 		qp->event(qp, event_type);
 		/* Need to put resource in event handler */
 		return NOTIFY_OK;
-	case MLX5_RES_DCT:
-		dct = (struct mlx5_core_dct *)common;
-		if (event_type == MLX5_EVENT_TYPE_DCT_DRAINED)
-			complete(&dct->drained);
-		break;
 	default:
 		break;
 	}
@@ -188,28 +193,15 @@ static void destroy_resource_common(struct mlx5_ib_dev *dev,
 }
 
 static int _mlx5_core_destroy_dct(struct mlx5_ib_dev *dev,
-				  struct mlx5_core_dct *dct, bool need_cleanup)
+				  struct mlx5_core_dct *dct)
 {
 	u32 in[MLX5_ST_SZ_DW(destroy_dct_in)] = {};
 	struct mlx5_core_qp *qp = &dct->mqp;
-	int err;
 
-	err = mlx5_core_drain_dct(dev, dct);
-	if (err) {
-		if (dev->mdev->state == MLX5_DEVICE_STATE_INTERNAL_ERROR)
-			goto destroy;
-
-		return err;
-	}
-	wait_for_completion(&dct->drained);
-destroy:
-	if (need_cleanup)
-		destroy_resource_common(dev, &dct->mqp);
 	MLX5_SET(destroy_dct_in, in, opcode, MLX5_CMD_OP_DESTROY_DCT);
 	MLX5_SET(destroy_dct_in, in, dctn, qp->qpn);
 	MLX5_SET(destroy_dct_in, in, uid, qp->uid);
-	err = mlx5_cmd_exec_in(dev->mdev, destroy_dct, in);
-	return err;
+	return mlx5_cmd_exec_in(dev->mdev, destroy_dct, in);
 }
 
 int mlx5_core_create_dct(struct mlx5_ib_dev *dev, struct mlx5_core_dct *dct,
@@ -227,13 +219,13 @@ int mlx5_core_create_dct(struct mlx5_ib_dev *dev, struct mlx5_core_dct *dct,
 
 	qp->qpn = MLX5_GET(create_dct_out, out, dctn);
 	qp->uid = MLX5_GET(create_dct_in, in, uid);
-	err = create_resource_common(dev, qp, MLX5_RES_DCT);
+	err = xa_err(xa_store_irq(&dev->qp_table.dct_xa, qp->qpn, dct, GFP_KERNEL));
 	if (err)
 		goto err_cmd;
 
 	return 0;
 err_cmd:
-	_mlx5_core_destroy_dct(dev, dct, false);
+	_mlx5_core_destroy_dct(dev, dct);
 	return err;
 }
 
@@ -284,7 +276,31 @@ static int mlx5_core_drain_dct(struct mlx5_ib_dev *dev,
 int mlx5_core_destroy_dct(struct mlx5_ib_dev *dev,
 			  struct mlx5_core_dct *dct)
 {
-	return _mlx5_core_destroy_dct(dev, dct, true);
+	struct mlx5_qp_table *table = &dev->qp_table;
+	struct mlx5_core_dct *tmp;
+	int err;
+
+	err = mlx5_core_drain_dct(dev, dct);
+	if (err) {
+		if (dev->mdev->state == MLX5_DEVICE_STATE_INTERNAL_ERROR)
+			goto destroy;
+
+		return err;
+	}
+	wait_for_completion(&dct->drained);
+
+destroy:
+	tmp = xa_cmpxchg_irq(&table->dct_xa, dct->mqp.qpn, dct, XA_ZERO_ENTRY, GFP_KERNEL);
+	if (WARN_ON(tmp != dct))
+		return xa_err(tmp) ?: -EINVAL;
+
+	err = _mlx5_core_destroy_dct(dev, dct);
+	if (err) {
+		xa_cmpxchg_irq(&table->dct_xa, dct->mqp.qpn, XA_ZERO_ENTRY, dct, 0);
+		return err;
+	}
+	xa_erase_irq(&table->dct_xa, dct->mqp.qpn);
+	return 0;
 }
 
 int mlx5_core_destroy_qp(struct mlx5_ib_dev *dev, struct mlx5_core_qp *qp)
@@ -488,6 +504,7 @@ int mlx5_init_qp_table(struct mlx5_ib_dev *dev)
 
 	spin_lock_init(&table->lock);
 	INIT_RADIX_TREE(&table->tree, GFP_ATOMIC);
+	xa_init(&table->dct_xa);
 	mlx5_qp_debugfs_init(dev->mdev);
 
 	table->nb.notifier_call = rsc_event_notifier;

include/linux/mlx5/driver.h

@@ -382,7 +382,6 @@ enum mlx5_res_type {
 	MLX5_RES_SRQ	= 3,
 	MLX5_RES_XSRQ	= 4,
 	MLX5_RES_XRQ	= 5,
-	MLX5_RES_DCT	= MLX5_EVENT_QUEUE_TYPE_DCT,
 };
 
 struct mlx5_core_rsc_common {