Re: [PATCH 05/17] nvme: wire-up support for async-passthru on char-device.

Paul Moore
2022-03-11T18:53:23Z

On Fri, Mar 11, 2022 at 12:56 PM Luis Chamberlain <mcgrof@kernel.org> wrote:
>
> On Tue, Mar 08, 2022 at 08:50:53PM +0530, Kanchan Joshi wrote:
> > diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
> > index 5c9cd9695519..1df270b47af5 100644
> > --- a/drivers/nvme/host/ioctl.c
> > +++ b/drivers/nvme/host/ioctl.c
> > @@ -369,6 +469,33 @@ long nvme_ns_chr_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> > return __nvme_ioctl(ns, cmd, (void __user *)arg);
> > }
> >
> > +static int nvme_ns_async_ioctl(struct nvme_ns *ns, struct io_uring_cmd *ioucmd)
> > +{
> > + int ret;
> > +
> > + BUILD_BUG_ON(sizeof(struct nvme_uring_cmd_pdu) > sizeof(ioucmd->pdu));
> > +
> > + switch (ioucmd->cmd_op) {
> > + case NVME_IOCTL_IO64_CMD:
> > + ret = nvme_user_cmd64(ns->ctrl, ns, NULL, ioucmd);
> > + break;
> > + default:
> > + ret = -ENOTTY;
> > + }
> > +
> > + if (ret >= 0)
> > + ret = -EIOCBQUEUED;
> > + return ret;
> > +}
>
> And here I think we'll need something like this:

If we can promise that we will have a LSM hook for all of the
file_operations::async_cmd implementations that are security relevant
we could skip the LSM passthrough hook at the io_uring layer. It
would potentially make life easier in that we don't have to worry
about putting the passthrough op in the right context, but risks
missing a LSM hook control point (it will happen at some point and
*boom* CVE).

> diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
> index ddb7e5864be6..83529adf130d 100644
> --- a/drivers/nvme/host/ioctl.c
> +++ b/drivers/nvme/host/ioctl.c
> @@ -5,6 +5,7 @@
> */
> #include <linux/ptrace.h> /* for force_successful_syscall_return */
> #include <linux/nvme_ioctl.h>
> +#include <linux/security.h>
> #include "nvme.h"
>
> /*
> @@ -524,6 +525,11 @@ static int nvme_ns_async_ioctl(struct nvme_ns *ns, struct io_uring_cmd *ioucmd)
>
> BUILD_BUG_ON(sizeof(struct nvme_uring_cmd_pdu) > sizeof(ioucmd->pdu));
>
> + ret = security_file_ioctl(ioucmd->file, ioucmd->cmd_op,
> + (unsigned long) ioucmd->cmd);
> + if (ret)
> + return ret;
> +
> switch (ioucmd->cmd_op) {
> case NVME_IOCTL_IO64_CMD:
> ret = nvme_user_cmd64(ns->ctrl, ns, NULL, ioucmd);

--
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