netdev - Re: [PATCH net 1/2] mlx5: fix possible ptp queue fifo overflow

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Date:   Mon, 23 Jan 2023 14:19:12 +0000
From:   Vadim Fedorenko <vadfed@...a.com>
To:     Leon Romanovsky <leon@...nel.org>
CC:     Aya Levin <ayal@...dia.com>, Saeed Mahameed <saeedm@...dia.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net 1/2] mlx5: fix possible ptp queue fifo overflow

On 23/01/2023 07:20, Leon Romanovsky wrote:
> 
> On Sun, Jan 22, 2023 at 08:16:01AM -0800, Vadim Fedorenko wrote:
>> Fifo pointers are not checked for overflow and this could potentially
>> lead to overflow and double free under heavy PTP traffic.
>>
>> Also there were accidental OOO cqe which lead to absolutely broken fifo.
>> Add checks to workaround OOO cqe and add counters to show the amount of
>> such events.
>>
>> Fixes: 19b43a432e3e ("net/mlx5e: Extend SKB room check to include PTP-SQ")
>> Signed-off-by: Vadim Fedorenko <vadfed@...a.com>
>> ---
>>   .../net/ethernet/mellanox/mlx5/core/en/ptp.c  | 28 ++++++++++++++-----
>>   .../net/ethernet/mellanox/mlx5/core/en/txrx.h |  6 +++-
>>   .../ethernet/mellanox/mlx5/core/en_stats.c    |  2 ++
>>   .../ethernet/mellanox/mlx5/core/en_stats.h    |  2 ++
>>   4 files changed, 30 insertions(+), 8 deletions(-)
> 
> <...>
> 
>> @@ -291,12 +291,16 @@ void mlx5e_skb_fifo_push(struct mlx5e_skb_fifo *fifo, struct sk_buff *skb)
>>   {
>>   	struct sk_buff **skb_item = mlx5e_skb_fifo_get(fifo, (*fifo->pc)++);
>>   
>> +	WARN_ONCE((u16)(*fifo->pc - *fifo->cc) > fifo->mask, "%s overflow", __func__);
> 
> nit, ""%s overflow", __func__" is not needed as call trace already includes function name.

yep, sure. But I still think we would like to have small tip about 
reasons. And also some other functions in mlx5 have the same debug info 
with WARN_ONCE.