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Subject: Re: [PATCH] RDMA/cma: Fix listener leak in rdma_cma_listen_on_all()
 failure
To:     Jason Gunthorpe <jgg@nvidia.com>, 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>
References: <20210913093344.17230-1-thomas.liu@ucloud.cn>
 <20210914195444.GA156389@nvidia.com>
From:   Mark Zhang <markzhang@nvidia.com>
Message-ID: <4b711688-9a82-03f1-844c-cf1557892679@nvidia.com>
Date:   Wed, 15 Sep 2021 14:34:19 +0800
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On 9/15/2021 3:54 AM, Jason Gunthorpe wrote:
> External email: Use caution opening links or attachments
> 
> 
> 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;

If this case is removed, is this code path still good?

cma_add_one/cma_remove_one
   cma_process_remove
     cma_send_device_removal_put
       cma_cancel_operation

>          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
>