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Date:   Tue, 14 Sep 2021 16:54:44 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Tao Liu <thomas.liu@ucloud.cn>
Cc:     dledford@redhat.com, leon@kernel.org, haakon.bugge@oracle.com,
        shayd@nvidia.com, avihaih@nvidia.com, linux-rdma@vger.kernel.org,
        linux-kernel@vger.kernel.org, thomas.liu@ucloud.com
Subject: Re: [PATCH] RDMA/cma: Fix listener leak in rdma_cma_listen_on_all()
 failure
Message-ID: <20210914195444.GA156389@nvidia.com>
References: <20210913093344.17230-1-thomas.liu@ucloud.cn>
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On Mon, Sep 13, 2021 at 05:33:44PM +0800, Tao Liu wrote:
> rdma_cma_listen_on_all() just destroy listener which lead to an error,
> but not including those already added in listen_list. Then cm state
> fallbacks to RDMA_CM_ADDR_BOUND.
> 
> When user destroys id, the listeners will not be destroyed, and
> process stucks.
> 
>  task:rping state:D stack:   0 pid:19605 ppid: 47036 flags:0x00000084
>  Call Trace:
>   __schedule+0x29a/0x780
>   ? free_unref_page_commit+0x9b/0x110
>   schedule+0x3c/0xa0
>   schedule_timeout+0x215/0x2b0
>   ? __flush_work+0x19e/0x1e0
>   wait_for_completion+0x8d/0xf0
>   _destroy_id+0x144/0x210 [rdma_cm]
>   ucma_close_id+0x2b/0x40 [rdma_ucm]
>   __destroy_id+0x93/0x2c0 [rdma_ucm]
>   ? __xa_erase+0x4a/0xa0
>   ucma_destroy_id+0x9a/0x120 [rdma_ucm]
>   ucma_write+0xb8/0x130 [rdma_ucm]
>   vfs_write+0xb4/0x250
>   ksys_write+0xb5/0xd0
>   ? syscall_trace_enter.isra.19+0x123/0x190
>   do_syscall_64+0x33/0x40
>   entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> Fixes: c80a0c52d85c ("RDMA/cma: Add missing error handling of listen_id")
> Signed-off-by: Tao Liu <thomas.liu@ucloud.cn>
> Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
>  drivers/infiniband/core/cma.c | 22 +++++++++++++++-------
>  1 file changed, 15 insertions(+), 7 deletions(-)

I'd like to see a bit more than this, I reworked the patch slightly
into this below. It is in for-rc so let me know if it busted up. Thanks

From a17a1faf5d3e2e19a75397dfd740dbde06f054c3 Mon Sep 17 00:00:00 2001
From: Tao Liu <thomas.liu@ucloud.cn>
Date: Mon, 13 Sep 2021 17:33:44 +0800
Subject: [PATCH] RDMA/cma: Fix listener leak in rdma_cma_listen_on_all()
 failure

If cma_listen_on_all() fails it leaves the per-device ID still on the
listen_list but the state is not set to RDMA_CM_ADDR_BOUND.

When the cmid is eventually destroyed cma_cancel_listens() is not called
due to the wrong state, however the per-device IDs are still holding the
refcount preventing the ID from being destroyed, thus deadlocking:

 task:rping state:D stack:   0 pid:19605 ppid: 47036 flags:0x00000084
 Call Trace:
  __schedule+0x29a/0x780
  ? free_unref_page_commit+0x9b/0x110
  schedule+0x3c/0xa0
  schedule_timeout+0x215/0x2b0
  ? __flush_work+0x19e/0x1e0
  wait_for_completion+0x8d/0xf0
  _destroy_id+0x144/0x210 [rdma_cm]
  ucma_close_id+0x2b/0x40 [rdma_ucm]
  __destroy_id+0x93/0x2c0 [rdma_ucm]
  ? __xa_erase+0x4a/0xa0
  ucma_destroy_id+0x9a/0x120 [rdma_ucm]
  ucma_write+0xb8/0x130 [rdma_ucm]
  vfs_write+0xb4/0x250
  ksys_write+0xb5/0xd0
  ? syscall_trace_enter.isra.19+0x123/0x190
  do_syscall_64+0x33/0x40
  entry_SYSCALL_64_after_hwframe+0x44/0xa9

Ensure that cma_listen_on_all() atomically unwinds its action under the
lock during error and reorganize how destroy_id works to be directly
sensitive to the listen list not indirectly through the state and some
other random collection of variables.

Fixes: c80a0c52d85c ("RDMA/cma: Add missing error handling of listen_id")
Link: https://lore.kernel.org/r/20210913093344.17230-1-thomas.liu@ucloud.cn
Signed-off-by: Tao Liu <thomas.liu@ucloud.cn>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 drivers/infiniband/core/cma.c | 28 ++++++++++++++++++++--------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
index 86ee3b01b3ee47..be6beee1dd4c5e 100644
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -1746,16 +1746,17 @@ static void cma_cancel_route(struct rdma_id_private *id_priv)
 	}
 }
 
-static void cma_cancel_listens(struct rdma_id_private *id_priv)
+static void _cma_cancel_listens(struct rdma_id_private *id_priv)
 {
 	struct rdma_id_private *dev_id_priv;
 
+	lockdep_assert_held(&lock);
+
 	/*
 	 * Remove from listen_any_list to prevent added devices from spawning
 	 * additional listen requests.
 	 */
-	mutex_lock(&lock);
-	list_del(&id_priv->list);
+	list_del_init(&id_priv->list);
 
 	while (!list_empty(&id_priv->listen_list)) {
 		dev_id_priv = list_entry(id_priv->listen_list.next,
@@ -1768,6 +1769,20 @@ static void cma_cancel_listens(struct rdma_id_private *id_priv)
 		rdma_destroy_id(&dev_id_priv->id);
 		mutex_lock(&lock);
 	}
+}
+
+static void cma_cancel_listens(struct rdma_id_private *id_priv)
+{
+	/*
+	 * During _destroy_id() it is not possible for this value to transition
+	 * from empty to !empty, test it outside to lock to avoid taking a
+	 * global lock on every destroy. Only listen all cases will have
+	 * something to do
+	 */
+	if (list_empty(&id_priv->list))
+		return;
+	mutex_lock(&lock);
+	_cma_cancel_listens(id_priv);
 	mutex_unlock(&lock);
 }
 
@@ -1781,10 +1796,6 @@ static void cma_cancel_operation(struct rdma_id_private *id_priv,
 	case RDMA_CM_ROUTE_QUERY:
 		cma_cancel_route(id_priv);
 		break;
-	case RDMA_CM_LISTEN:
-		if (cma_any_addr(cma_src_addr(id_priv)) && !id_priv->cma_dev)
-			cma_cancel_listens(id_priv);
-		break;
 	default:
 		break;
 	}
@@ -1855,6 +1866,7 @@ static void cma_leave_mc_groups(struct rdma_id_private *id_priv)
 static void _destroy_id(struct rdma_id_private *id_priv,
 			enum rdma_cm_state state)
 {
+	cma_cancel_listens(id_priv);
 	cma_cancel_operation(id_priv, state);
 
 	rdma_restrack_del(&id_priv->res);
@@ -2579,7 +2591,7 @@ static int cma_listen_on_all(struct rdma_id_private *id_priv)
 	return 0;
 
 err_listen:
-	list_del(&id_priv->list);
+	_cma_cancel_listens(id_priv);
 	mutex_unlock(&lock);
 	if (to_destroy)
 		rdma_destroy_id(&to_destroy->id);
-- 
2.33.0