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

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Date: Fri, 27 Oct 2023 14:58:54 +0800
From: Dust Li <dust.li@...ux.alibaba.com>
To: Wojciech Drewek <wojciech.drewek@...el.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 Wed, Oct 25, 2023 at 11:06:25AM +0200, Wojciech Drewek wrote:
>
>
>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.

You are right.

The original version is mlx5e_encap_put, I mistakenly used the name of
the old version when doing git blame.

Best regards,
Dust


>
>> 
>> 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);