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

[Yishai Hadas <yishaih@nvidia.com>]

On 30/06/2025 20:28, Alex Williamson wrote:
> On Sun, 29 Jun 2025 09:58:43 +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 max_msg_size up to u64 so multiplication will
>> be extended to u64.
> 
> Personally I'd go with changing the multiplier to 4ULL rather than
> changing the storage size here, but let's wait for Yishai and Jason.
> Thanks,
> 
> Alex
> 

Yes, let's go with Alex's suggestion.

max_msg_size based on the CAP, can't be larger than u32.

Yishai

>> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>>
>> Signed-off-by: Artem Sadovnikov <a.sadovnikov@ispras.ru>
>> ---
>>   drivers/vfio/pci/mlx5/cmd.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/vfio/pci/mlx5/cmd.c b/drivers/vfio/pci/mlx5/cmd.c
>> index 5b919a0b2524..0bdaf1d23a78 100644
>> --- a/drivers/vfio/pci/mlx5/cmd.c
>> +++ b/drivers/vfio/pci/mlx5/cmd.c
>> @@ -1503,7 +1503,7 @@ int mlx5vf_start_page_tracker(struct vfio_device *vdev,
>>   	struct mlx5_vhca_qp *fw_qp;
>>   	struct mlx5_core_dev *mdev;
>>   	u32 log_max_msg_size;
>> -	u32 max_msg_size;
>> +	u64 max_msg_size;
>>   	u64 rq_size = SZ_2M;
>>   	u32 max_recv_wr;
>>   	int err;
>