Re: [PATCH v2] vfio/mlx5: fix possible overflow in tracking max message size

[Yishai Hadas <yishaih@nvidia.com>]

On 12/07/2025 0:00, Alex Williamson wrote:
> On Tue,  1 Jul 2025 14:40:17 +0000
> Artem Sadovnikov <a.sadovnikov@ispras.ru> wrote:
> 
>> MLX cap pg_track_log_max_msg_size consists of 5 bits, value of which is
>> used as power of 2 for max_msg_size. This can lead to multiplication
>> overflow between max_msg_size (u32) and integer constant, and afterwards
>> incorrect value is being written to rq_size.
>>
>> Fix this issue by extending integer constant to u64 type.
>>
>> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>>
>> Suggested-by: Alex Williamson <alex.williamson@redhat.com>
>> Signed-off-by: Artem Sadovnikov <a.sadovnikov@ispras.ru>
>> ---
>> Changes from v1:
>> - The constant type was changed instead of variable type.
>> - The patch name was accidentally cut and is now fixed.
>> - LKML: https://lore.kernel.org/all/20250629095843.13349-1-a.sadovnikov@ispras.ru/
>> ---
>>   drivers/vfio/pci/mlx5/cmd.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/vfio/pci/mlx5/cmd.c b/drivers/vfio/pci/mlx5/cmd.c
>> index 5b919a0b2524..a92b095b90f6 100644
>> --- a/drivers/vfio/pci/mlx5/cmd.c
>> +++ b/drivers/vfio/pci/mlx5/cmd.c
>> @@ -1523,8 +1523,8 @@ int mlx5vf_start_page_tracker(struct vfio_device *vdev,
>>   	log_max_msg_size = MLX5_CAP_ADV_VIRTUALIZATION(mdev, pg_track_log_max_msg_size);
>>   	max_msg_size = (1ULL << log_max_msg_size);
>>   	/* The RQ must hold at least 4 WQEs/messages for successful QP creation */
>> -	if (rq_size < 4 * max_msg_size)
>> -		rq_size = 4 * max_msg_size;
>> +	if (rq_size < 4ULL * max_msg_size)
>> +		rq_size = 4ULL * max_msg_size;
>>   
>>   	memset(tracker, 0, sizeof(*tracker));
>>   	tracker->uar = mlx5_get_uars_page(mdev);
> 
> LGTM, Yishai?  Thanks,
> 
> Alex
> 

Reviewed-by: Yishai Hadas <yishaih@nvidia.com>