linux-kernel - Re: [PATCH v2] RDMA/rxe: Prevent from double freeing rxe_map

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Date:   Tue, 28 Dec 2021 17:10:59 +0800
From:   Zhu Yanjun <zyjzyj2000@...il.com>
To:     Li Zhijian <lizhijian@...fujitsu.com>
Cc:     Jason Gunthorpe <jgg@...pe.ca>,
        RDMA mailing list <linux-rdma@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, yanjun.zhu@...ux.dev,
        Bob Pearson <rpearsonhpe@...il.com>,
        Jason Gunthorpe <jgg@...dia.com>
Subject: Re: [PATCH v2] RDMA/rxe: Prevent from double freeing rxe_map_set

On Tue, Dec 28, 2021 at 9:39 AM Li Zhijian <lizhijian@...fujitsu.com> wrote:
>
> a same rxe_map_set could be freed twice:
> rxe_reg_user_mr()
>   -> rxe_mr_init_user()
>     -> rxe_mr_free_map_set() # 1st
>   -> rxe_drop_ref()
>    ...
>     -> rxe_mr_cleanup()
>       -> rxe_mr_free_map_set() # 2nd
>
> By convention, we should cleanup/free resources in the error path in the
> same function where the resources are alloted in. So rxe_mr_init_user()
> doesn't need to free the map_set directly.
>
> In addition, we have to reset map_set to NULL inside rxe_mr_alloc() if needed
> to prevent from map_set being double freed in rxe_mr_cleanup().
>
> CC: Jason Gunthorpe <jgg@...dia.com>
> Signed-off-by: Li Zhijian <lizhijian@...fujitsu.com>

Thanks.

Acked-by: Zhu Yanjun <zyjzyj2000@...il.com>

Zhu Yanjun
> ---
> V2: Fix it by a simpler way by following suggestion from Bob,
> ---
>  drivers/infiniband/sw/rxe/rxe_mr.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/infiniband/sw/rxe/rxe_mr.c b/drivers/infiniband/sw/rxe/rxe_mr.c
> index 25c78aade822..7c4cd19a9db2 100644
> --- a/drivers/infiniband/sw/rxe/rxe_mr.c
> +++ b/drivers/infiniband/sw/rxe/rxe_mr.c
> @@ -141,6 +141,7 @@ static int rxe_mr_alloc(struct rxe_mr *mr, int num_buf, int both)
>                 ret = rxe_mr_alloc_map_set(num_map, &mr->next_map_set);
>                 if (ret) {
>                         rxe_mr_free_map_set(mr->num_map, mr->cur_map_set);
> +                       mr->cur_map_set = NULL;
>                         goto err_out;
>                 }
>         }
> @@ -214,7 +215,7 @@ int rxe_mr_init_user(struct rxe_pd *pd, u64 start, u64 length, u64 iova,
>                                 pr_warn("%s: Unable to get virtual address\n",
>                                                 __func__);
>                                 err = -ENOMEM;
> -                               goto err_cleanup_map;
> +                               goto err_release_umem;
>                         }
>
>                         buf->addr = (uintptr_t)vaddr;
> @@ -237,8 +238,6 @@ int rxe_mr_init_user(struct rxe_pd *pd, u64 start, u64 length, u64 iova,
>
>         return 0;
>
> -err_cleanup_map:
> -       rxe_mr_free_map_set(mr->num_map, mr->cur_map_set);
>  err_release_umem:
>         ib_umem_release(umem);
>  err_out:
> --
> 2.31.1
>
>
>