Re: [PATCH for-next 2/2] nvme: Make CAP_SYS_ADMIN fine-granular

[Christoph Hellwig <hch@lst.de>]

On Mon, Sep 26, 2022 at 08:24:30PM +0530, Kanchan Joshi wrote:
> Change all the callers of CAP_SYS_ADMIN to go through nvme_cmd_allowed
> for any decision making.
> Since file open mode is taken into consideration for any
> approval/denial, change at various places to keep file-mode information
> handy.
> 
> Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
> ---
>  drivers/nvme/host/ioctl.c | 70 +++++++++++++++++++++------------------
>  1 file changed, 38 insertions(+), 32 deletions(-)
> 
> diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
> index 6ca6477dd899..4e53a01e702d 100644
> --- a/drivers/nvme/host/ioctl.c
> +++ b/drivers/nvme/host/ioctl.c
> @@ -259,7 +259,7 @@ static bool nvme_validate_passthru_nsid(struct nvme_ctrl *ctrl,
>  }
>  
>  static int nvme_user_cmd(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
> -			struct nvme_passthru_cmd __user *ucmd)
> +			struct nvme_passthru_cmd __user *ucmd, fmode_t mode)
>  {
>  	struct nvme_passthru_cmd cmd;
>  	struct nvme_command c;
> @@ -267,10 +267,10 @@ static int nvme_user_cmd(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
>  	u64 result;
>  	int status;
>  
> -	if (!capable(CAP_SYS_ADMIN))
> -		return -EACCES;
>  	if (copy_from_user(&cmd, ucmd, sizeof(cmd)))
>  		return -EFAULT;
> +	if (!nvme_cmd_allowed(ns, cmd.opcode, mode))
> +		return -EACCES;

Btw, what speaks against moving this check a little bit later,
so that we can pass the nvme_command to nvme_cmd_allowed, and thus
can simply use nvme_is_write?