Re: [PATCH v3 2/3] xen/privcmd: Add IOCTL_PRIVCMD_DM_OP

From: Stefano Stabellini
Date: Tue Feb 14 2017 - 13:39:17 EST

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On Tue, 14 Feb 2017, Boris Ostrovsky wrote:
> On 02/13/2017 12:03 PM, Paul Durrant wrote:
> > 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.
> >
> > NOTE: There is no requirement for user-space code to bounce data through
> > locked memory buffers (as with IOCTL_PRIVCMD_HYPERCALL) since
> > privcmd has enough information to lock the original buffers
> > directly.
> >
> > [1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=524a98c2
> >
> > Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
>
>
> Stefano,
>
> Are you OK with ARM changes?

Yes:

Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

Thanks for CC'ing me, I missed the patch.

>
>
> > ---
> > Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> > Cc: Juergen Gross <jgross@xxxxxxxx>
> >
> > v3:
> > - Add module parameters for max number of dm_op buffers and max buffer
> > size
> > - Fix arm build
> > - Fix commit comment to reflect re-worked patch
> >
> > v2:
> > - Lock the user pages rather than bouncing through kernel memory
> > ---
> > arch/arm/xen/enlighten.c | 1 +
> > arch/arm/xen/hypercall.S | 1 +
> > arch/arm64/xen/hypercall.S | 1 +
> > arch/x86/include/asm/xen/hypercall.h | 7 ++
> > drivers/xen/privcmd.c | 139 +++++++++++++++++++++++++++++++++++
> > include/uapi/xen/privcmd.h | 13 ++++
> > include/xen/arm/hypercall.h | 1 +
> > include/xen/interface/hvm/dm_op.h | 32 ++++++++
> > include/xen/interface/xen.h | 1 +
> > 9 files changed, 196 insertions(+)
> > create mode 100644 include/xen/interface/hvm/dm_op.h
> >
> > diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> > index 11d9f28..81e3217 100644
> > --- a/arch/arm/xen/enlighten.c
> > +++ b/arch/arm/xen/enlighten.c
> > @@ -457,4 +457,5 @@ EXPORT_SYMBOL_GPL(HYPERVISOR_tmem_op);
> > EXPORT_SYMBOL_GPL(HYPERVISOR_platform_op);
> > EXPORT_SYMBOL_GPL(HYPERVISOR_multicall);
> > EXPORT_SYMBOL_GPL(HYPERVISOR_vm_assist);
> > +EXPORT_SYMBOL_GPL(HYPERVISOR_dm_op);
> > EXPORT_SYMBOL_GPL(privcmd_call);
> > diff --git a/arch/arm/xen/hypercall.S b/arch/arm/xen/hypercall.S
> > index a648dfc..b0b80c0 100644
> > --- a/arch/arm/xen/hypercall.S
> > +++ b/arch/arm/xen/hypercall.S
> > @@ -92,6 +92,7 @@ HYPERCALL1(tmem_op);
> > HYPERCALL1(platform_op_raw);
> > HYPERCALL2(multicall);
> > HYPERCALL2(vm_assist);
> > +HYPERCALL3(dm_op);
> >
> > ENTRY(privcmd_call)
> > stmdb sp!, {r4}
> > diff --git a/arch/arm64/xen/hypercall.S b/arch/arm64/xen/hypercall.S
> > index 947830a..401ceb7 100644
> > --- a/arch/arm64/xen/hypercall.S
> > +++ b/arch/arm64/xen/hypercall.S
> > @@ -84,6 +84,7 @@ HYPERCALL1(tmem_op);
> > HYPERCALL1(platform_op_raw);
> > HYPERCALL2(multicall);
> > HYPERCALL2(vm_assist);
> > +HYPERCALL3(dm_op);
> >
> > ENTRY(privcmd_call)
> > mov x16, x0
> > 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 5e5c7ae..a33f17e 100644
> > --- a/drivers/xen/privcmd.c
> > +++ b/drivers/xen/privcmd.c
> > @@ -22,6 +22,7 @@
> > #include <linux/pagemap.h>
> > #include <linux/seq_file.h>
> > #include <linux/miscdevice.h>
> > +#include <linux/moduleparam.h>
> >
> > #include <asm/pgalloc.h>
> > #include <asm/pgtable.h>
> > @@ -32,6 +33,7 @@
> > #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>
> > @@ -43,6 +45,17 @@ MODULE_LICENSE("GPL");
> >
> > #define PRIV_VMA_LOCKED ((void *)1)
> >
> > +unsigned int privcmd_dm_op_max_num = 16;
> > +module_param_named(dm_op_max_nr_bufs, privcmd_dm_op_max_num, uint, 0644);
> > +MODULE_PARM_DESC(dm_op_max_nr_bufs,
> > + "Maximum number of buffers per dm_op hypercall");
> > +
> > +unsigned int privcmd_dm_op_buf_max_size = XEN_PAGE_SIZE;
> > +module_param_named(dm_op_buf_max_size, privcmd_dm_op_buf_max_size, uint,
> > + 0644);
> > +MODULE_PARM_DESC(dm_op_buf_max_size,
> > + "Maximum size of a dm_op hypercall buffer");
> > +
> > static int privcmd_vma_range_is_mapped(
> > struct vm_area_struct *vma,
> > unsigned long addr,
> > @@ -548,6 +561,128 @@ static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
> > goto out;
> > }
> >
> > +static int lock_pages(
> > + struct privcmd_dm_op_buf kbufs[], unsigned int num,
> > + struct page *pages[], unsigned int nr_pages)
> > +{
> > + unsigned int i;
> > +
> > + for (i = 0; i < num; i++) {
> > + unsigned int requested;
> > + int pinned;
> > +
> > + requested = DIV_ROUND_UP(
> > + offset_in_page(kbufs[i].uptr) + kbufs[i].size,
> > + PAGE_SIZE);
> > + if (requested > nr_pages)
> > + return -ENOSPC;
> > +
> > + pinned = get_user_pages_fast(
> > + (unsigned long) kbufs[i].uptr,
> > + requested, FOLL_WRITE, pages);
> > + if (pinned < 0)
> > + return pinned;
> > +
> > + nr_pages -= pinned;
> > + pages += pinned;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static void unlock_pages(struct page *pages[], unsigned int nr_pages)
> > +{
> > + unsigned int i;
> > +
> > + if (!pages)
> > + return;
> > +
> > + for (i = 0; i < nr_pages; i++) {
> > + if (pages[i])
> > + put_page(pages[i]);
> > + }
> > +}
> > +
> > +static long privcmd_ioctl_dm_op(void __user *udata)
> > +{
> > + struct privcmd_dm_op kdata;
> > + struct privcmd_dm_op_buf *kbufs;
> > + unsigned int nr_pages = 0;
> > + struct page **pages = 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;
> > +
> > + if (kdata.num > privcmd_dm_op_max_num)
> > + return -E2BIG;
> > +
> > + 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;
> > + }
> > +
> > + for (i = 0; i < kdata.num; i++) {
> > + if (kbufs[i].size > privcmd_dm_op_buf_max_size) {
> > + rc = -E2BIG;
> > + goto out;
> > + }
> > +
> > + if (!access_ok(VERIFY_WRITE, kbufs[i].uptr,
> > + kbufs[i].size)) {
> > + rc = -EFAULT;
> > + goto out;
> > + }
> > +
> > + nr_pages += DIV_ROUND_UP(
> > + offset_in_page(kbufs[i].uptr) + kbufs[i].size,
> > + PAGE_SIZE);
> > + }
> > +
> > + pages = kcalloc(nr_pages, sizeof(*pages), GFP_KERNEL);
> > + if (!pages) {
> > + rc = -ENOMEM;
> > + goto out;
> > + }
> > +
> > + xbufs = kcalloc(kdata.num, sizeof(*xbufs), GFP_KERNEL);
> > + if (!xbufs) {
> > + rc = -ENOMEM;
> > + goto out;
> > + }
> > +
> > + rc = lock_pages(kbufs, kdata.num, pages, nr_pages);
> > + if (rc)
> > + goto out;
> > +
> > + for (i = 0; i < kdata.num; i++) {
> > + set_xen_guest_handle(xbufs[i].h, kbufs[i].uptr);
> > + xbufs[i].size = kbufs[i].size;
> > + }
> > +
> > + xen_preemptible_hcall_begin();
> > + rc = HYPERVISOR_dm_op(kdata.dom, kdata.num, xbufs);
> > + xen_preemptible_hcall_end();
> > +
> > +out:
> > + unlock_pages(pages, nr_pages);
> > + kfree(xbufs);
> > + kfree(pages);
> > + kfree(kbufs);
> > +
> > + return rc;
> > +}
> > +
> > static long privcmd_ioctl(struct file *file,
> > unsigned int cmd, unsigned long data)
> > {
> > @@ -571,6 +706,10 @@ 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/arm/hypercall.h b/include/xen/arm/hypercall.h
> > index 9d874db..73db4b2 100644
> > --- a/include/xen/arm/hypercall.h
> > +++ b/include/xen/arm/hypercall.h
> > @@ -53,6 +53,7 @@ int HYPERVISOR_physdev_op(int cmd, void *arg);
> > int HYPERVISOR_vcpu_op(int cmd, int vcpuid, void *extra_args);
> > int HYPERVISOR_tmem_op(void *arg);
> > int HYPERVISOR_vm_assist(unsigned int cmd, unsigned int type);
> > +int HYPERVISOR_dm_op(domid_t domid, unsigned int nr_bufs, void *bufs);
> > int HYPERVISOR_platform_op_raw(void *arg);
> > static inline int HYPERVISOR_platform_op(struct xen_platform_op *op)
> > {
> > 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
>

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