RE: [PATCH 2/3] xen/privcmd: Add IOCTL_PRIVCMD_DM_OP

From: Paul Durrant
Date: Thu Feb 09 2017 - 09:28:26 EST

Next message: Masami Hiramatsu: "Re: [RFC][PATCH 00/21] tracing: Inter-event (e.g. latency) support"
Previous message: Marek Szyprowski: "[PATCH v8 0/3] DMA Engine: switch PL330 driver to non-irq-safe runtime PM"
In reply to: Paul Durrant: "[PATCH 2/3] xen/privcmd: Add IOCTL_PRIVCMD_DM_OP"
Next in thread: Boris Ostrovsky: "Re: [PATCH 2/3] xen/privcmd: Add IOCTL_PRIVCMD_DM_OP"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

> -----Original Message-----
> From: Paul Durrant [mailto:paul.durrant@xxxxxxxxxx]
> Sent: 09 February 2017 14:18
> To: xen-devel@xxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Cc: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; Boris Ostrovsky
> <boris.ostrovsky@xxxxxxxxxx>; Juergen Gross <jgross@xxxxxxxx>
> Subject: [PATCH 2/3] xen/privcmd: Add IOCTL_PRIVCMD_DM_OP
>
> Recently a new dm_op[1] hypercall was added to Xen to provide a
> mechanism
> for restricting device emulators (such as QEMU) to a limited set of
> hypervisor operations, and being able to audit those operations in the
> kernel of the domain in which they run.
>
> This patch adds IOCTL_PRIVCMD_DM_OP as gateway for
> __HYPERVISOR_dm_op,
> bouncing the callers buffers through kernel memory to allow the address
> ranges to be audited (and negating the need to bounce through locked
> memory in user-space).

Actually, it strikes me (now that I've posted the patch) that I should probably just mlock the user buffers rather than bouncing them through kernel... Anyway, I'd still appreciate review on other aspects of the patch.

Paul

>
> [1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=524a98c2
>
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> ---
> Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Cc: Juergen Gross <jgross@xxxxxxxx>
> ---
> arch/x86/include/asm/xen/hypercall.h | 7 ++
> drivers/xen/privcmd.c | 122
> +++++++++++++++++++++++++++++++++++
> include/uapi/xen/privcmd.h | 13 ++++
> include/xen/interface/hvm/dm_op.h | 32 +++++++++
> include/xen/interface/xen.h | 1 +
> 5 files changed, 175 insertions(+)
> create mode 100644 include/xen/interface/hvm/dm_op.h
>
> diff --git a/arch/x86/include/asm/xen/hypercall.h
> b/arch/x86/include/asm/xen/hypercall.h
> index a12a047..f6d20f6 100644
> --- a/arch/x86/include/asm/xen/hypercall.h
> +++ b/arch/x86/include/asm/xen/hypercall.h
> @@ -472,6 +472,13 @@ HYPERVISOR_xenpmu_op(unsigned int op, void
> *arg)
> return _hypercall2(int, xenpmu_op, op, arg);
> }
>
> +static inline int
> +HYPERVISOR_dm_op(
> + domid_t dom, unsigned int nr_bufs, void *bufs)
> +{
> + return _hypercall3(int, dm_op, dom, nr_bufs, bufs);
> +}
> +
> static inline void
> MULTI_fpu_taskswitch(struct multicall_entry *mcl, int set)
> {
> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> index b4e5e27..31c43f4 100644
> --- a/drivers/xen/privcmd.c
> +++ b/drivers/xen/privcmd.c
> @@ -32,6 +32,7 @@
> #include <xen/xen.h>
> #include <xen/privcmd.h>
> #include <xen/interface/xen.h>
> +#include <xen/interface/hvm/dm_op.h>
> #include <xen/features.h>
> #include <xen/page.h>
> #include <xen/xen-ops.h>
> @@ -548,6 +549,123 @@ static long privcmd_ioctl_mmap_batch(void __user
> *udata, int version)
> goto out;
> }
>
> +static int bounce_in(struct privcmd_dm_op_buf kbufs[], void *kptr[],
> + unsigned int num)
> +{
> + unsigned int i;
> + int rc = 0;
> +
> + for (i = 0; i < num; i++) {
> + kptr[i] = kzalloc(kbufs[i].size, GFP_KERNEL);
> + if (!kptr[i]) {
> + rc = -ENOMEM;
> + break;
> + }
> +
> + if (copy_from_user(kptr[i], kbufs[i].uptr, kbufs[i].size)) {
> + rc = -EFAULT;
> + break;
> + }
> + }
> +
> + return rc;
> +}
> +
> +static int bounce_out(struct privcmd_dm_op_buf kbufs[], void *kptr[],
> + unsigned int num)
> +{
> + unsigned int i;
> + int rc = 0;
> +
> + for (i = 0; i < num; i++)
> + if (copy_to_user(kbufs[i].uptr, kptr[i], kbufs[i].size))
> + rc = -EFAULT;
> +
> + return rc;
> +}
> +
> +static void free_kptr(void *kptr[], unsigned int num)
> +{
> + unsigned int i;
> +
> + if (!kptr)
> + return;
> +
> + for (i = 0; i < num; i++)
> + kfree(kptr[i]);
> +
> + kfree(kptr);
> +}
> +
> +static long privcmd_ioctl_dm_op(void __user *udata)
> +{
> + struct privcmd_dm_op kdata;
> + struct privcmd_dm_op_buf *kbufs;
> + void **kptr = NULL;
> + struct xen_dm_op_buf *xbufs = NULL;
> + unsigned int i;
> + long rc;
> +
> + if (copy_from_user(&kdata, udata, sizeof(kdata)))
> + return -EFAULT;
> +
> + if (kdata.num == 0)
> + return 0;
> +
> + /*
> + * Set a tolerable upper limit on the number of buffers
> + * without being overly restrictive, since we can't easily
> + * predict what future dm_ops may require.
> + */
> + if (kdata.num * sizeof(*kbufs) > PAGE_SIZE)
> + return -EINVAL;
> +
> + kbufs = kcalloc(kdata.num, sizeof(*kbufs), GFP_KERNEL);
> + if (!kbufs)
> + return -ENOMEM;
> +
> + if (copy_from_user(kbufs, kdata.ubufs,
> + sizeof(*kbufs) * kdata.num)) {
> + rc = -EFAULT;
> + goto out;
> + }
> +
> + kptr = kcalloc(kdata.num, sizeof(*kptr), GFP_KERNEL);
> + if (!kptr) {
> + rc = -ENOMEM;
> + goto out;
> + }
> +
> + rc = bounce_in(kbufs, kptr, kdata.num);
> + if (rc)
> + goto out;
> +
> + xbufs = kcalloc(kdata.num, sizeof(*xbufs), GFP_KERNEL);
> + if (!xbufs) {
> + rc = -ENOMEM;
> + goto out;
> + }
> +
> + for (i = 0; i < kdata.num; i++) {
> + set_xen_guest_handle(xbufs[i].h, kptr[i]);
> + xbufs[i].size = kbufs[i].size;
> + }
> +
> + xen_preemptible_hcall_begin();
> + rc = HYPERVISOR_dm_op(kdata.dom, kdata.num, xbufs);
> + xen_preemptible_hcall_end();
> +
> + if (!rc)
> + rc = bounce_out(kbufs, kptr, kdata.num);
> +
> +out:
> + kfree(xbufs);
> + free_kptr(kptr, kdata.num);
> + kfree(kbufs);
> +
> + return rc;
> +}
> +
> static long privcmd_ioctl(struct file *file,
> unsigned int cmd, unsigned long data)
> {
> @@ -571,6 +689,10 @@ static long privcmd_ioctl(struct file *file,
> ret = privcmd_ioctl_mmap_batch(udata, 2);
> break;
>
> + case IOCTL_PRIVCMD_DM_OP:
> + ret = privcmd_ioctl_dm_op(udata);
> + break;
> +
> default:
> break;
> }
> diff --git a/include/uapi/xen/privcmd.h b/include/uapi/xen/privcmd.h
> index 7ddeeda..f8c5d75 100644
> --- a/include/uapi/xen/privcmd.h
> +++ b/include/uapi/xen/privcmd.h
> @@ -77,6 +77,17 @@ struct privcmd_mmapbatch_v2 {
> int __user *err; /* array of error codes */
> };
>
> +struct privcmd_dm_op_buf {
> + void __user *uptr;
> + size_t size;
> +};
> +
> +struct privcmd_dm_op {
> + domid_t dom;
> + __u16 num;
> + const struct privcmd_dm_op_buf __user *ubufs;
> +};
> +
> /*
> * @cmd: IOCTL_PRIVCMD_HYPERCALL
> * @arg: &privcmd_hypercall_t
> @@ -98,5 +109,7 @@ struct privcmd_mmapbatch_v2 {
> _IOC(_IOC_NONE, 'P', 3, sizeof(struct privcmd_mmapbatch))
> #define IOCTL_PRIVCMD_MMAPBATCH_V2 \
> _IOC(_IOC_NONE, 'P', 4, sizeof(struct privcmd_mmapbatch_v2))
> +#define IOCTL_PRIVCMD_DM_OP \
> + _IOC(_IOC_NONE, 'P', 5, sizeof(struct privcmd_dm_op))
>
> #endif /* __LINUX_PUBLIC_PRIVCMD_H__ */
> diff --git a/include/xen/interface/hvm/dm_op.h
> b/include/xen/interface/hvm/dm_op.h
> new file mode 100644
> index 0000000..ee9e480
> --- /dev/null
> +++ b/include/xen/interface/hvm/dm_op.h
> @@ -0,0 +1,32 @@
> +/*
> + * Copyright (c) 2016, Citrix Systems Inc
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> copy
> + * of this software and associated documentation files (the "Software"), to
> + * deal in the Software without restriction, including without limitation the
> + * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
> + * sell copies of the Software, and to permit persons to whom the Software
> is
> + * furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
> EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
> MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO
> EVENT SHALL THE
> + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
> OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> OTHER
> + * DEALINGS IN THE SOFTWARE.
> + */
> +
> +#ifndef __XEN_PUBLIC_HVM_DM_OP_H__
> +#define __XEN_PUBLIC_HVM_DM_OP_H__
> +
> +struct xen_dm_op_buf {
> + GUEST_HANDLE(void) h;
> + xen_ulong_t size;
> +};
> +DEFINE_GUEST_HANDLE_STRUCT(xen_dm_op_buf);
> +
> +#endif /* __XEN_PUBLIC_HVM_DM_OP_H__ */
> diff --git a/include/xen/interface/xen.h b/include/xen/interface/xen.h
> index 1b0d189..4f4830e 100644
> --- a/include/xen/interface/xen.h
> +++ b/include/xen/interface/xen.h
> @@ -81,6 +81,7 @@
> #define __HYPERVISOR_tmem_op 38
> #define __HYPERVISOR_xc_reserved_op 39 /* reserved for XenClient */
> #define __HYPERVISOR_xenpmu_op 40
> +#define __HYPERVISOR_dm_op 41
>
> /* Architecture-specific hypercall definitions. */
> #define __HYPERVISOR_arch_0 48
> --
> 2.1.4

Next message: Masami Hiramatsu: "Re: [RFC][PATCH 00/21] tracing: Inter-event (e.g. latency) support"
Previous message: Marek Szyprowski: "[PATCH v8 0/3] DMA Engine: switch PL330 driver to non-irq-safe runtime PM"
In reply to: Paul Durrant: "[PATCH 2/3] xen/privcmd: Add IOCTL_PRIVCMD_DM_OP"
Next in thread: Boris Ostrovsky: "Re: [PATCH 2/3] xen/privcmd: Add IOCTL_PRIVCMD_DM_OP"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]