netdev - Re: [PATCH] net/mlx5e: fix a potential double-free in fs_any_create

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Date: Tue, 28 Nov 2023 10:58:04 +0200
From: Tariq Toukan <ttoukan.linux@...il.com>
To: Dinghao Liu <dinghao.liu@....edu.cn>
Cc: Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Zhengchao Shao <shaozhengchao@...wei.com>,
 Rahul Rameshbabu <rrameshbabu@...dia.com>, Simon Horman <horms@...nel.org>,
 Tariq Toukan <tariqt@...dia.com>, Aya Levin <ayal@...dia.com>,
 netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
 linux-kernel@...r.kernel.org, Tariq Toukan <tariqt@...dia.com>
Subject: Re: [PATCH] net/mlx5e: fix a potential double-free in
 fs_any_create_groups

On 28/11/2023 10:28, Dinghao Liu wrote:
> When kcalloc() for ft->g succeeds but kvzalloc() for in fails,
> fs_any_create_groups() will free ft->g. However, its caller
> fs_any_create_table() will free ft->g again through calling
> mlx5e_destroy_flow_table(), which will lead to a double-free.
> Fix this by removing the kfree(ft->g) in fs_any_create_groups().
> 
> Fixes: 0f575c20bf06 ("net/mlx5e: Introduce Flow Steering ANY API")
> Signed-off-by: Dinghao Liu <dinghao.liu@....edu.cn>
> ---
>   drivers/net/ethernet/mellanox/mlx5/core/en/fs_tt_redirect.c | 1 -
>   1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/fs_tt_redirect.c b/drivers/net/ethernet/mellanox/mlx5/core/en/fs_tt_redirect.c
> index be83ad9db82a..b222d23bfb9a 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en/fs_tt_redirect.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en/fs_tt_redirect.c
> @@ -434,7 +434,6 @@ static int fs_any_create_groups(struct mlx5e_flow_table *ft)
>   	ft->g = kcalloc(MLX5E_FS_UDP_NUM_GROUPS, sizeof(*ft->g), GFP_KERNEL);
>   	in = kvzalloc(inlen, GFP_KERNEL);
>   	if  (!in || !ft->g) {
> -		kfree(ft->g);
>   		kvfree(in);
>   		return -ENOMEM;
>   	}

Function fs_any_create_groups should not return failure without cleaning 
itself up. This is not the right fix.
Freeing ft->g and setting it to NULL will do it, and will avoid the 
double free.