Re: [PATCH v1 1/1] platform/mellanox: fix potential race in mlxbf-tmfifo driver

[Hans de Goede]

Hi,

On 5/9/23 11:35, Vadim Pasternak wrote:
> 
> 
>> -----Original Message-----
>> From: Liming Sun <limings@xxxxxxxxxx>
>> Sent: Wednesday, 26 April 2023 17:24
>> To: Vadim Pasternak <vadimp@xxxxxxxxxx>; David Thompson
>> <davthompson@xxxxxxxxxx>; Hans de Goede <hdegoede@xxxxxxxxxx>;
>> Mark Gross <markgross@xxxxxxxxxx>
>> Cc: Liming Sun <limings@xxxxxxxxxx>; platform-driver-x86@xxxxxxxxxxxxxxx;
>> linux-kernel@xxxxxxxxxxxxxxx
>> Subject: [PATCH v1 1/1] platform/mellanox: fix potential race in mlxbf-tmfifo
>> driver
>>
>> This commit adds memory barrier for the 'vq' update in function
>> mlxbf_tmfifo_virtio_find_vqs() to avoid potential race due to out-of-order
>> memory write. It also adds barrier for the 'is_ready'
>> flag to make sure the initializations are visible before this flag is checked.
>>
>> Signed-off-by: Liming Sun <limings@xxxxxxxxxx>
> 
> Reviewed-by: Vadim Pasternak <vadimp@xxxxxxxxxx>

Thank you for your patch, I've applied this patch to my fixes
branch:
https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/log/?h=fixes

Note it will show up in my fixes branch once I've pushed my
local branch there, which might take a while.

I will include this patch in my next fixes pull-req to Linus
for the current kernel development cycle.

Regards,

Hans



>> ---
>>  drivers/platform/mellanox/mlxbf-tmfifo.c | 11 +++++++++--
>>  1 file changed, 9 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/platform/mellanox/mlxbf-tmfifo.c
>> b/drivers/platform/mellanox/mlxbf-tmfifo.c
>> index 91a077c35b8b..a79318e90a13 100644
>> --- a/drivers/platform/mellanox/mlxbf-tmfifo.c
>> +++ b/drivers/platform/mellanox/mlxbf-tmfifo.c
>> @@ -784,7 +784,7 @@ static void mlxbf_tmfifo_rxtx(struct
>> mlxbf_tmfifo_vring *vring, bool is_rx)
>>  	fifo = vring->fifo;
>>
>>  	/* Return if vdev is not ready. */
>> -	if (!fifo->vdev[devid])
>> +	if (!fifo || !fifo->vdev[devid])
>>  		return;
>>
>>  	/* Return if another vring is running. */ @@ -980,9 +980,13 @@
>> static int mlxbf_tmfifo_virtio_find_vqs(struct virtio_device *vdev,
>>
>>  		vq->num_max = vring->num;
>>
>> +		vq->priv = vring;
>> +
>> +		/* Make vq update visible before using it. */
>> +		virtio_mb(false);
>> +
>>  		vqs[i] = vq;
>>  		vring->vq = vq;
>> -		vq->priv = vring;
>>  	}
>>
>>  	return 0;
>> @@ -1302,6 +1306,9 @@ static int mlxbf_tmfifo_probe(struct
>> platform_device *pdev)
>>
>>  	mod_timer(&fifo->timer, jiffies + MLXBF_TMFIFO_TIMER_INTERVAL);
>>
>> +	/* Make all updates visible before setting the 'is_ready' flag. */
>> +	virtio_mb(false);
>> +
>>  	fifo->is_ready = true;
>>  	return 0;
>>
>> --
>> 2.30.1
>