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

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Message-ID: <20250630112831.2207fa2e.alex.williamson@redhat.com>
Date: Mon, 30 Jun 2025 11:28:31 -0600
From: Alex Williamson <alex.williamson@...hat.com>
To: Artem Sadovnikov <a.sadovnikov@...ras.ru>
Cc: kvm@...r.kernel.org, Yishai Hadas <yishaih@...dia.com>, Jason Gunthorpe
 <jgg@...pe.ca>, Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>,
 Kevin Tian <kevin.tian@...el.com>, linux-kernel@...r.kernel.org,
 lvc-project@...uxtesting.org
Subject: Re: [PATCH] vfio/mlx5: fix possible overflow in tracking max

On Sun, 29 Jun 2025 09:58:43 +0000
Artem Sadovnikov <a.sadovnikov@...ras.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

> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Signed-off-by: Artem Sadovnikov <a.sadovnikov@...ras.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;