Re: [PATCH rdma-next] RDMA/restrack: Delay QP deletion till all users are gone

[Jason Gunthorpe <jgg@nvidia.com>]

On Sun, Apr 18, 2021 at 04:37:35PM +0300, Leon Romanovsky wrote:
> From: Shay Drory <shayd@nvidia.com>
> 
> Currently, in case of QP, the following use-after-free is possible:
> 
> 	cpu0				cpu1
> 	----				----
>  res_get_common_dumpit()
>  rdma_restrack_get()
>  fill_res_qp_entry()
> 				ib_destroy_qp_user()
> 				 rdma_restrack_del()
> 				 qp->device->ops.destroy_qp()
>   ib_query_qp()
>   qp->device->ops.query_qp()
>     --> use-after-free-qp
> 
> This is because rdma_restrack_del(), in case of QP, isn't waiting until
> all users are gone.
> 
> Fix it by making rdma_restrack_del() wait until all users are gone for
> QPs as well.
> 
> Fixes: 13ef5539def7 ("RDMA/restrack: Count references to the verbs objects")
> Signed-off-by: Shay Drory <shayd@nvidia.com>
> Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
> ---
>  drivers/infiniband/core/restrack.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/infiniband/core/restrack.c b/drivers/infiniband/core/restrack.c
> index ffabaf327242..def0c5b0efe9 100644
> --- a/drivers/infiniband/core/restrack.c
> +++ b/drivers/infiniband/core/restrack.c
> @@ -340,7 +340,7 @@ void rdma_restrack_del(struct rdma_restrack_entry *res)
>  	rt = &dev->res[res->type];
>  
>  	old = xa_erase(&rt->xa, res->id);
> -	if (res->type == RDMA_RESTRACK_MR || res->type == RDMA_RESTRACK_QP)
> +	if (res->type == RDMA_RESTRACK_MR)
>  		return;

Why is MR skipping this?


It also calls into the driver under its dumpit, at the very least this
needs a comment.

Jason