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libvmmapi: Provide an interface for limiting rights on the device fd

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Currently libvmmapi provides a way to get a list of the allowed ioctls
on the vmm device file, so that bhyve can limit rights on the device
file fd.  The interface is rather strange: it allocates a copy of the
list but returns a const pointer, so the caller has to cast away the
const in order to free it without aggravating the compiler.

As far as I can see, there's no reason to make a copy of the array, but
changing vm_get_ioctls() to not do that would break compatibility.  So
this change just introduces a better interface: move all rights-limiting
logic into libvmmapi.

Any new operations on the fd should be wrapped by libvmmapi, so also
discourage use of vm_get_device_fd().  Currently bhyve uses it only when
limiting rights on the device fd.

No functional change intended.

Reviewed by:	jhb
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D37098
This commit is contained in:
Mark Johnston 2022-10-24 17:31:11 -04:00
parent 16295b0a5a
commit 3e9b4532d1
2 changed files with 54 additions and 25 deletions
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68
lib/libvmmapi/vmmapi.c
View file

@ -32,6 +32,7 @@
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/capsicum.h>
#include <sys/sysctl.h>
#include <sys/ioctl.h>
#include <sys/linker.h>
@ -43,6 +44,7 @@ __FBSDID("$FreeBSD$");
#include <x86/segments.h>
#include <machine/specialreg.h>
#include <capsicum_helpers.h>
#include <errno.h>
#include <stdbool.h>
#include <stdio.h>
@ -1729,6 +1731,49 @@ vm_get_topology(struct vmctx *ctx,
return (error);
}
/* Keep in sync with machine/vmm_dev.h. */
static const cap_ioctl_t vm_ioctl_cmds[] = { VM_RUN, VM_SUSPEND, VM_REINIT,
VM_ALLOC_MEMSEG, VM_GET_MEMSEG, VM_MMAP_MEMSEG, VM_MMAP_MEMSEG,
VM_MMAP_GETNEXT, VM_MUNMAP_MEMSEG, VM_SET_REGISTER, VM_GET_REGISTER,
VM_SET_SEGMENT_DESCRIPTOR, VM_GET_SEGMENT_DESCRIPTOR,
VM_SET_REGISTER_SET, VM_GET_REGISTER_SET,
VM_SET_KERNEMU_DEV, VM_GET_KERNEMU_DEV,
VM_INJECT_EXCEPTION, VM_LAPIC_IRQ, VM_LAPIC_LOCAL_IRQ,
VM_LAPIC_MSI, VM_IOAPIC_ASSERT_IRQ, VM_IOAPIC_DEASSERT_IRQ,
VM_IOAPIC_PULSE_IRQ, VM_IOAPIC_PINCOUNT, VM_ISA_ASSERT_IRQ,
VM_ISA_DEASSERT_IRQ, VM_ISA_PULSE_IRQ, VM_ISA_SET_IRQ_TRIGGER,
VM_SET_CAPABILITY, VM_GET_CAPABILITY, VM_BIND_PPTDEV,
VM_UNBIND_PPTDEV, VM_MAP_PPTDEV_MMIO, VM_PPTDEV_MSI,
VM_PPTDEV_MSIX, VM_UNMAP_PPTDEV_MMIO, VM_PPTDEV_DISABLE_MSIX,
VM_INJECT_NMI, VM_STATS, VM_STAT_DESC,
VM_SET_X2APIC_STATE, VM_GET_X2APIC_STATE,
VM_GET_HPET_CAPABILITIES, VM_GET_GPA_PMAP, VM_GLA2GPA,
VM_GLA2GPA_NOFAULT,
VM_ACTIVATE_CPU, VM_GET_CPUS, VM_SUSPEND_CPU, VM_RESUME_CPU,
VM_SET_INTINFO, VM_GET_INTINFO,
VM_RTC_WRITE, VM_RTC_READ, VM_RTC_SETTIME, VM_RTC_GETTIME,
VM_RESTART_INSTRUCTION, VM_SET_TOPOLOGY, VM_GET_TOPOLOGY
};
int
vm_limit_rights(struct vmctx *ctx)
{
cap_rights_t rights;
size_t ncmds;
cap_rights_init(&rights, CAP_IOCTL, CAP_MMAP_RW);
if (caph_rights_limit(ctx->fd, &rights) != 0)
return (-1);
ncmds = nitems(vm_ioctl_cmds);
if (caph_ioctls_limit(ctx->fd, vm_ioctl_cmds, ncmds) != 0)
return (-1);
return (0);
}
/*
* Avoid using in new code. Operations on the fd should be wrapped here so that
* capability rights can be kept in sync.
*/
int
vm_get_device_fd(struct vmctx *ctx)
{
@ -1736,32 +1781,11 @@ vm_get_device_fd(struct vmctx *ctx)
return (ctx->fd);
}
/* Legacy interface, do not use. */
const cap_ioctl_t *
vm_get_ioctls(size_t *len)
{
cap_ioctl_t *cmds;
/* keep in sync with machine/vmm_dev.h */
static const cap_ioctl_t vm_ioctl_cmds[] = { VM_RUN, VM_SUSPEND, VM_REINIT,
VM_ALLOC_MEMSEG, VM_GET_MEMSEG, VM_MMAP_MEMSEG, VM_MMAP_MEMSEG,
VM_MMAP_GETNEXT, VM_MUNMAP_MEMSEG, VM_SET_REGISTER, VM_GET_REGISTER,
VM_SET_SEGMENT_DESCRIPTOR, VM_GET_SEGMENT_DESCRIPTOR,
VM_SET_REGISTER_SET, VM_GET_REGISTER_SET,
VM_SET_KERNEMU_DEV, VM_GET_KERNEMU_DEV,
VM_INJECT_EXCEPTION, VM_LAPIC_IRQ, VM_LAPIC_LOCAL_IRQ,
VM_LAPIC_MSI, VM_IOAPIC_ASSERT_IRQ, VM_IOAPIC_DEASSERT_IRQ,
VM_IOAPIC_PULSE_IRQ, VM_IOAPIC_PINCOUNT, VM_ISA_ASSERT_IRQ,
VM_ISA_DEASSERT_IRQ, VM_ISA_PULSE_IRQ, VM_ISA_SET_IRQ_TRIGGER,
VM_SET_CAPABILITY, VM_GET_CAPABILITY, VM_BIND_PPTDEV,
VM_UNBIND_PPTDEV, VM_MAP_PPTDEV_MMIO, VM_PPTDEV_MSI,
VM_PPTDEV_MSIX, VM_UNMAP_PPTDEV_MMIO, VM_PPTDEV_DISABLE_MSIX,
VM_INJECT_NMI, VM_STATS, VM_STAT_DESC,
VM_SET_X2APIC_STATE, VM_GET_X2APIC_STATE,
VM_GET_HPET_CAPABILITIES, VM_GET_GPA_PMAP, VM_GLA2GPA,
VM_GLA2GPA_NOFAULT,
VM_ACTIVATE_CPU, VM_GET_CPUS, VM_SUSPEND_CPU, VM_RESUME_CPU,
VM_SET_INTINFO, VM_GET_INTINFO,
VM_RTC_WRITE, VM_RTC_READ, VM_RTC_SETTIME, VM_RTC_GETTIME,
VM_RESTART_INSTRUCTION, VM_SET_TOPOLOGY, VM_GET_TOPOLOGY };
if (len == NULL) {
cmds = malloc(sizeof(vm_ioctl_cmds));

11
lib/libvmmapi/vmmapi.h
View file

@ -118,10 +118,10 @@ int vm_mmap_memseg(struct vmctx *ctx, vm_paddr_t gpa, int segid,
int vm_munmap_memseg(struct vmctx *ctx, vm_paddr_t gpa, size_t len);
int vm_create(const char *name);
int vm_get_device_fd(struct vmctx *ctx);
struct vmctx *vm_open(const char *name);
void vm_close(struct vmctx *ctx);
void vm_destroy(struct vmctx *ctx);
int vm_limit_rights(struct vmctx *ctx);
int vm_parse_memsize(const char *optarg, size_t *memsize);
int vm_setup_memory(struct vmctx *ctx, size_t len, enum vm_mmap_style s);
void *vm_map_gpa(struct vmctx *ctx, vm_paddr_t gaddr, size_t len);
@ -195,8 +195,6 @@ int vm_disable_pptdev_msix(struct vmctx *ctx, int bus, int slot, int func);
int vm_get_intinfo(struct vmctx *ctx, int vcpu, uint64_t *i1, uint64_t *i2);
int vm_set_intinfo(struct vmctx *ctx, int vcpu, uint64_t exit_intinfo);
const cap_ioctl_t *vm_get_ioctls(size_t *len);
/*
* Return a pointer to the statistics buffer. Note that this is not MT-safe.
*/
@ -266,6 +264,13 @@ void vm_setup_freebsd_gdt(uint64_t *gdtr);
*/
int vm_snapshot_req(struct vm_snapshot_meta *meta);
int vm_restore_time(struct vmctx *ctx);
/*
* Deprecated interfaces, do not use them in new code.
*/
int vm_get_device_fd(struct vmctx *ctx);
const cap_ioctl_t *vm_get_ioctls(size_t *len);
__END_DECLS
#endif /* _VMMAPI_H_ */