linux-kernel - Re: [PATCH] RDMA/mlx5: Fix memory leak

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Date:   Sun, 13 Mar 2022 21:06:56 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Yongzhi Liu <lyz_cs@....edu.cn>
Cc:     jgg@...pe.ca, yishaih@...lanox.com, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org, fuyq@....pku.edu.cn
Subject: Re: [PATCH] RDMA/mlx5: Fix memory leak

On Fri, Mar 11, 2022 at 09:06:01AM -0800, Yongzhi Liu wrote:
> [why]
> xa_insert is failed, so caller of subscribe_event_xa_alloc
> cannot call other function to free obj_event. Therefore,
> Resource release is needed on the error handling path to
> prevent memory leak.
> 
> [how]
> Fix this by adding kfree on the error handling path.
> 
> Fixes: 7597385 ("IB/mlx5: Enable subscription for device events over DEVX")
> 
> Signed-off-by: Yongzhi Liu <lyz_cs@....edu.cn>
> ---
>  drivers/infiniband/hw/mlx5/devx.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

The change itself is correct one, but commit message needs to be improved.
Something like that:

------------------------------------------------------------------
[PATCH] RDMA/mlx5: Fix memory leak in error subscribe event routine

In case second xa_insert() fails, the obj_event is not released.
Fix the error unwind flow to free that memory to avoid memory leak.

Fixes: 7597385 ("IB/mlx5: Enable subscription for device events over DEVX")
Signed-off-by: Yongzhi Liu <lyz_cs@....edu.cn>
-------------------------------------------------------------------

> 
> diff --git a/drivers/infiniband/hw/mlx5/devx.c b/drivers/infiniband/hw/mlx5/devx.c
> index 08b7f6b..15c0884 100644
> --- a/drivers/infiniband/hw/mlx5/devx.c
> +++ b/drivers/infiniband/hw/mlx5/devx.c
> @@ -1886,8 +1886,10 @@ subscribe_event_xa_alloc(struct mlx5_devx_event_table *devx_event_table,
>  				key_level2,
>  				obj_event,
>  				GFP_KERNEL);
> -		if (err)
> +		if (err) {
> +			kfree(obj_event);
>  			return err;
> +		}
>  		INIT_LIST_HEAD(&obj_event->obj_sub_list);
>  	}
>  
> -- 
> 2.7.4
>