Re: [PATCH rdma-next] RDMA/addr: Fix race with netevent_callback()/rdma_addr_cancel()

[Jason Gunthorpe <jgg@nvidia.com>]

On Wed, Sep 30, 2020 at 10:20:07AM +0300, Leon Romanovsky wrote:
> From: Jason Gunthorpe <jgg@nvidia.com>
> 
> This three thread race can result in the work being run once the callback
> becomes NULL:
> 
>        CPU1                 CPU2                   CPU3
>  netevent_callback()
>                      process_one_req()       rdma_addr_cancel()
>                       [..]
>      spin_lock_bh()
>   	set_timeout()
>      spin_unlock_bh()
> 
> 						spin_lock_bh()
> 						list_del_init(&req->list);
> 						spin_unlock_bh()
> 
> 		     req->callback = NULL
> 		     spin_lock_bh()
> 		       if (!list_empty(&req->list))
>                          // Skipped!
> 		         // cancel_delayed_work(&req->work);
> 		     spin_unlock_bh()
> 
> 		    process_one_req() // again
> 		     req->callback() // BOOM
> 						cancel_delayed_work_sync()
> 
> The solution is to always cancel the work once it is completed so any
> in between set_timeout() does not result in it running again.
> 
> Fixes: 44e75052bc2a ("RDMA/rdma_cm: Make rdma_addr_cancel into a fence")
> Reported-by: Dan Aloni <dan@kernelim.com>
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
> ---
>  drivers/infiniband/core/addr.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)

Applied to for-next

Jason