linux-kernel - Re: [PATCH v5 0/6] nvdimm: Add an IOCTL pass thru for DSM calls

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Date:	Wed, 6 Jan 2016 15:58:22 -0800
From:	Dan Williams <dan.j.williams@...el.com>
To:	Jerry Hoemann <jerry.hoemann@....com>
Cc:	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <lenb@...nel.org>,
	"Elliott, Robert (Persistent Memory)" <elliott@....com>,
	jmoyer <jmoyer@...hat.com>,
	Dmitry Krivenok <krivenok.dmitry@...il.com>,
	Linda Knippers <linda.knippers@....com>,
	Robert Moore <robert.moore@...el.com>,
	Lv Zheng <lv.zheng@...el.com>,
	Rafael J Wysocki <rafael.j.wysocki@...el.com>,
	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
	Linux ACPI <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 0/6] nvdimm: Add an IOCTL pass thru for DSM calls

On Wed, Jan 6, 2016 at 3:03 PM, Jerry Hoemann <jerry.hoemann@....com> wrote:
> The NVDIMM code in the kernel supports an IOCTL interface to user
> space based upon the Intel Example DSM:
>
>         http://pmem.io/documents/NVDIMM_DSM_Interface_Example.pdf
>
> This interface cannot be used by other NVDIMM DSMs that support
> incompatible functions.
>
> This patch set adds a generic "passthru" IOCTL interface which
> is not tied to a particular DSM.
>
> A new _IOC_NR ND_CMD_CALL_DSM == "10" is added for the pass thru call.
>
> The new data structure nd_cmd_dsmcall_pkg serves as a wrapper for
> the passthru calls.  This wrapper supplies the data that the kernel
> needs to make the _DSM call.
>
> Unlike the definitions of the _DSM functions themselves, the nd_cmd_dsmcall_pkg
> provides the calling information (input/output sizes) in an uniform
> manner making the kernel marshaling of the arguments straight
> forward.
>
> This shifts the marshaling burden from the kernel to the user
> space application while still permitting the kernel to internally
> call _DSM functions.
>
> The kernel functions __nd_ioctl and acpi_nfit_ctl were modified
> to accomodate ND_CMD_CALL_DSM.
>
>
> Changes in version 5:
> ---------------------
> 0. Fixed submit comment for drivers/acpi/utils.c.
>
>
> Changes in version 4:
> ---------------------
> 0. Added patch to correct parameter type passed to acpi_evaluate_dsm
>    ACPI defines arguments rev and fun as 64 bit quanties and the ioctl
>    exports to user face rev and func. We want those to match the ACPI spec.
>
>    Also modified acpi_evaluate_dsm_typed and acpi_check dsm which had
>    similar issue.
>
> 1. nd_cmd_dsmcall_pkg rearange a reserve and rounded up total size
>    to 16 byte boundary.
>
> 2. Created stand alone patch for the pre-existing security issue related
>    to "read only" IOCTL calls.
>
> 3. Added patch for increasing envelope size of IOCTL.  Needed to
>    be able to read in the wrapper to know remaining size to copy in.
>
>    Note: in_env, out_env are statics sized based upon this change.
>
> 4. Moved copyin code to table driven nd_cmd_desc
>
>   Note, the last 40 lines or so of acpi_nfit_ctl will not return _DSM
>   data unless the size allocated in user space buffer equals
>   out_obj->buffer.length.
>
>   The semantic we want in the pass thru case is to return as much
>   of the _DSM data as the user space buffer would accomodate.
>
>   Hence, in acpi_nfit_ctl I have retained the line:
>
>                 memcpy(pkg->dsm_buf + pkg->h.dsm_in,
>                         out_obj->buffer.pointer,
>                         min(pkg->h.dsm_size, pkg->h.dsm_out));
>
>   and the early return from the function.
>
>
>
>
> Changes in version 3:
> ---------------------
> 1. Changed name ND_CMD_PASSTHRU to ND_CMD_CALL_DSM.
>
> 2. Value of ND_CMD_CALL_DSM is 10, not 100.
>
> 3. Changed name of nd_passthru_pkg to nd_cmd_dsmcall_pkg.
>
> 4. Removed separate functions for handling ND_CMD_CALL_DSM.
>    Moved functionality to __nd_ioctl and acpi_nfit_ctl proper.
>    The resultant code looks very different from prior versions.
>
> 5. BUGFIX: __nd_ioctl: Change the if read_only switch to use
>          _IOC_NR cmd (not ioctl_cmd) for better protection.
>
>         Do we want to make a stand alone patch for this issue?
>
>
> Changes in version 2:
> ---------------------
> 1. Cleanup access mode check in nd_ioctl and nvdimm_ioctl.
> 2. Change name of ndn_pkg to nd_passthru_pkg
> 3. Adjust sizes in nd_passthru_pkg. DSM intergers are 64 bit.
> 4. No new ioctl type, instead tunnel into the existing number space.
> 5. Push down one function level where determine ioctl cmd type.
> 6. re-work diagnostic print/dump message in pass-thru functions.
>
>
>
>
> Jerry Hoemann (6):
>   ACPI / util: Fix acpi_evaluate_dsm() argument type
>   nvdimm: Clean-up access mode check.
>   nvdimm: Add wrapper for IOCTL pass thru
>   nvdimm: Fix security issue with DSM IOCTL.
>   nvdimm: Increase max envelope size for IOCTL
>   nvdimm: Add IOCTL pass thru functions

These look good to me.

I'll tag "nvdimm: Fix security issue with DSM IOCTL." for -stable.

Thanks Jerry!
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