[RFC 1/2] nvme: add whitelisting infrastructure

[Joel Granados]

On Fri, Sep 09, 2022 at 10:03:06PM +0530, Kanchan Joshi wrote:
> If CAP_SYS_ADMIN is present, nothing else is checked, as before.
> If CAP_SYS_ADMIN is not present, take the decision based on
> - type of nvme command (io or admin)
> - nature of nvme-command (write or read)
> - mode with which file was opened (read-only, read-write etc.)
> 
> io-commands that write/read are allowed only if matching file mode is
> present.
> for admin-commands, few read-only admin command are allowed and that too
> when mode matches.
> 
> Signed-off-by: Kanchan Joshi <joshi.k at samsung.com>
> ---
>  drivers/nvme/host/ioctl.c | 36 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
> 
> diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
> index 548aca8b5b9f..0d99135a1745 100644
> --- a/drivers/nvme/host/ioctl.c
> +++ b/drivers/nvme/host/ioctl.c
> @@ -20,6 +20,42 @@ static void __user *nvme_to_user_ptr(uintptr_t ptrval)
>  	return (void __user *)ptrval;
>  }
>  
> +bool nvme_io_cmd_allowed(u8 opcode, fmode_t mode)
These all should be static functions. right? So we keep the scope within
the file?

Best
> +{
> +	/* allow write/read based on what was allowed for open */
> +	/* TBD: try to use nvme_is_write() here */
> +	if (opcode & 1)
> +		return (mode & FMODE_WRITE);
> +	else
> +		return (mode & FMODE_READ);
> +}
> +
> +bool nvme_admin_cmd_allowed(u8 opcode, fmode_t mode)
> +{
> +	/* allowed few read-only commands post the mode check */
> +	switch (opcode) {
> +	case nvme_admin_identify:
> +	case nvme_admin_get_log_page:
> +	case nvme_admin_get_features:
> +		return (mode & FMODE_READ);
> +	default:
> +		return false;
> +	}
> +}
> +
> +bool nvme_cmd_allowed(struct nvme_ns *ns, u8 opcode, fmode_t mode)
> +{
> +	bool ret;
> +	/* root can do anything */
> +	if (capable(CAP_SYS_ADMIN))
> +		return true;
> +	if (ns == NULL)
> +		ret = nvme_admin_cmd_allowed(opcode, mode);
> +	else
> +		ret = nvme_io_cmd_allowed(opcode, mode);
> +	return ret;
> +}
> +
>  static void *nvme_add_user_metadata(struct bio *bio, void __user *ubuf,
>  		unsigned len, u32 seed, bool write)
>  {
> -- 
> 2.25.1
> 
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