linux-kernel - Re: [PATCH net] net/mlx5e: fix double free of encap

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Date:   Wed, 25 Oct 2023 11:06:25 +0200
From:   Wojciech Drewek <wojciech.drewek@...el.com>
To:     Dust Li <dust.li@...ux.alibaba.com>,
        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>
CC:     <netdev@...r.kernel.org>, <linux-rdma@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Cruz Zhao <cruzzhao@...ux.alibaba.com>,
        Tianchen Ding <dtcccc@...ux.alibaba.com>
Subject: Re: [PATCH net] net/mlx5e: fix double free of encap_header



On 25.10.2023 05:27, Dust Li wrote:
> When mlx5_packet_reformat_alloc() fails, the encap_header allocated in
> mlx5e_tc_tun_create_header_ipv4{6} will be released within it. However,
> e->encap_header is already set to the previously freed encap_header
> before mlx5_packet_reformat_alloc(). As a result, the later
> mlx5e_encap_put() will free e->encap_header again, causing a double free
> issue.
> 
> mlx5e_encap_put()
>     --> mlx5e_encap_dealloc()
>         --> kfree(e->encap_header)

nit: I think it should mlx5e_encap_put_locked not mlx5e_encap_put to be precise.

> 
> This happens when cmd: MLX5_CMD_OP_ALLOC_PACKET_REFORMAT_CONTEXT fail.
> 
> This patch fix it by not setting e->encap_header until
> mlx5_packet_reformat_alloc() success.
> 
> Fixes: d589e785baf5e("net/mlx5e: Allow concurrent creation of encap entries")
> Reported-by: Cruz Zhao <cruzzhao@...ux.alibaba.com>
> Reported-by: Tianchen Ding <dtcccc@...ux.alibaba.com>
> Signed-off-by: Dust Li <dust.li@...ux.alibaba.com>
> ---

Reviewed-by: Wojciech Drewek <wojciech.drewek@...el.com>

>  drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun.c b/drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun.c
> index 00a04fdd756f..8bca696b6658 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun.c
> @@ -300,9 +300,6 @@ int mlx5e_tc_tun_create_header_ipv4(struct mlx5e_priv *priv,
>  	if (err)
>  		goto destroy_neigh_entry;
>  
> -	e->encap_size = ipv4_encap_size;
> -	e->encap_header = encap_header;
> -
>  	if (!(nud_state & NUD_VALID)) {
>  		neigh_event_send(attr.n, NULL);
>  		/* the encap entry will be made valid on neigh update event
> @@ -322,6 +319,8 @@ int mlx5e_tc_tun_create_header_ipv4(struct mlx5e_priv *priv,
>  		goto destroy_neigh_entry;
>  	}
>  
> +	e->encap_size = ipv4_encap_size;
> +	e->encap_header = encap_header;
>  	e->flags |= MLX5_ENCAP_ENTRY_VALID;
>  	mlx5e_rep_queue_neigh_stats_work(netdev_priv(attr.out_dev));
>  	mlx5e_route_lookup_ipv4_put(&attr);
> @@ -568,9 +567,6 @@ int mlx5e_tc_tun_create_header_ipv6(struct mlx5e_priv *priv,
>  	if (err)
>  		goto destroy_neigh_entry;
>  
> -	e->encap_size = ipv6_encap_size;
> -	e->encap_header = encap_header;
> -
>  	if (!(nud_state & NUD_VALID)) {
>  		neigh_event_send(attr.n, NULL);
>  		/* the encap entry will be made valid on neigh update event
> @@ -590,6 +586,8 @@ int mlx5e_tc_tun_create_header_ipv6(struct mlx5e_priv *priv,
>  		goto destroy_neigh_entry;
>  	}
>  
> +	e->encap_size = ipv6_encap_size;
> +	e->encap_header = encap_header;
>  	e->flags |= MLX5_ENCAP_ENTRY_VALID;
>  	mlx5e_rep_queue_neigh_stats_work(netdev_priv(attr.out_dev));
>  	mlx5e_route_lookup_ipv6_put(&attr);