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vmm: Validate credentials when opening a vmmdev

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Rather than performing privilege checks after a specific VM's device
file is opened, do it once at the time the device file is opened.  This
means that one can continue to access a VM via its device fd after
attaching to a jail which does not have vmm enabled, but this seems like
a reasonable semantic to have anyway.

Reviewed by:	jhb
Differential Revision:	https://reviews.freebsd.org/D46486
This commit is contained in:
Mark Johnston 2024-09-01 14:00:32 +00:00
parent 133a513ddc
commit 4008758105
1 changed files with 27 additions and 12 deletions
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39
sys/dev/vmm/vmm_dev.c
View file

@ -186,10 +186,6 @@ vmmdev_rw(struct cdev *cdev, struct uio *uio, int flags)
void *hpa, *cookie;
struct vmmdev_softc *sc;
error = vmm_priv_check(curthread->td_ucred);
if (error)
return (error);
sc = vmmdev_lookup2(cdev);
if (sc == NULL)
return (ENXIO);
@ -327,6 +323,32 @@ vm_set_register_set(struct vcpu *vcpu, unsigned int count, int *regnum,
return (error);
}
static int
vmmdev_open(struct cdev *dev, int flags, int fmt, struct thread *td)
{
struct vmmdev_softc *sc;
int error;
sc = vmmdev_lookup2(dev);
KASSERT(sc != NULL, ("%s: device not found", __func__));
/*
* A user can only access VMs that they themselves have created.
*/
if (td->td_ucred != sc->ucred)
return (EPERM);
/*
* A jail without vmm access shouldn't be able to access vmm device
* files at all, but check here just to be thorough.
*/
error = vmm_priv_check(td->td_ucred);
if (error != 0)
return (error);
return (0);
}
static const struct vmmdev_ioctl vmmdev_ioctls[] = {
VMMDEV_IOCTL(VM_GET_REGISTER, VMMDEV_IOCTL_LOCK_ONE_VCPU),
VMMDEV_IOCTL(VM_SET_REGISTER, VMMDEV_IOCTL_LOCK_ONE_VCPU),
@ -375,10 +397,6 @@ vmmdev_ioctl(struct cdev *cdev, u_long cmd, caddr_t data, int fflag,
const struct vmmdev_ioctl *ioctl;
int error, vcpuid;
error = vmm_priv_check(td->td_ucred);
if (error)
return (error);
sc = vmmdev_lookup2(cdev);
if (sc == NULL)
return (ENXIO);
@ -681,10 +699,6 @@ vmmdev_mmap_single(struct cdev *cdev, vm_ooffset_t *offset, vm_size_t mapsize,
int error, found, segid;
bool sysmem;
error = vmm_priv_check(curthread->td_ucred);
if (error)
return (error);
first = *offset;
last = first + mapsize;
if ((nprot & PROT_EXEC) || first < 0 || first >= last)
@ -833,6 +847,7 @@ SYSCTL_PROC(_hw_vmm, OID_AUTO, destroy,
static struct cdevsw vmmdevsw = {
.d_name = "vmmdev",
.d_version = D_VERSION,
.d_open = vmmdev_open,
.d_ioctl = vmmdev_ioctl,
.d_mmap_single = vmmdev_mmap_single,
.d_read = vmmdev_rw,