On Sat, 7 Mar 2020 01:04:41 +0000 "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote: > > From: Alex Williamson <alex.williamson@xxxxxxxxxx> > > Sent: Friday, March 6, 2020 11:39 PM > > > > On Fri, 6 Mar 2020 08:32:40 +0000 > > "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote: > > > > > > From: Alex Williamson <alex.williamson@xxxxxxxxxx> > > > > Sent: Friday, March 6, 2020 2:18 AM > > > > > > > > On Tue, 25 Feb 2020 02:59:37 +0000 > > > > "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote: > > > > > > > > > > From: Alex Williamson > > > > > > Sent: Thursday, February 20, 2020 2:54 AM > > > > > > > > > > > > If we enable SR-IOV on a vfio-pci owned PF, the resulting VFs are not > > > > > > fully isolated from the PF. The PF can always cause a denial of service > > > > > > to the VF, even if by simply resetting itself. The degree to which a PF > > > > > > can access the data passed through a VF or interfere with its > > operation > > > > > > is dependent on a given SR-IOV implementation. Therefore we want > > to > > > > > > avoid a scenario where an existing vfio-pci based userspace driver > > might > > > > > > assume the PF driver is trusted, for example assigning a PF to one VM > > > > > > and VF to another with some expectation of isolation. IOMMU > > grouping > > > > > > could be a solution to this, but imposes an unnecessarily strong > > > > > > relationship between PF and VF drivers if they need to operate with > > the > > > > > > same IOMMU context. Instead we introduce a "VF token", which is > > > > > > essentially just a shared secret between PF and VF drivers, > > implemented > > > > > > as a UUID. > > > > > > > > > > > > The VF token can be set by a vfio-pci based PF driver and must be > > known > > > > > > by the vfio-pci based VF driver in order to gain access to the device. > > > > > > This allows the degree to which this VF token is considered secret to > > be > > > > > > determined by the applications and environment. For example a VM > > > > might > > > > > > generate a random UUID known only internally to the hypervisor > > while a > > > > > > userspace networking appliance might use a shared, or even well > > know, > > > > > > UUID among the application drivers. > > > > > > > > > > > > To incorporate this VF token, the VFIO_GROUP_GET_DEVICE_FD > > interface > > > > is > > > > > > extended to accept key=value pairs in addition to the device name. > > This > > > > > > allows us to most easily deny user access to the device without risk > > > > > > that existing userspace drivers assume region offsets, IRQs, and other > > > > > > device features, leading to more elaborate error paths. The format of > > > > > > these options are expected to take the form: > > > > > > > > > > > > "$DEVICE_NAME $OPTION1=$VALUE1 $OPTION2=$VALUE2" > > > > > > > > > > > > Where the device name is always provided first for compatibility and > > > > > > additional options are specified in a space separated list. The > > > > > > relation between and requirements for the additional options will be > > > > > > vfio bus driver dependent, however unknown or unused option > > within > > > > this > > > > > > schema should return error. This allow for future use of unknown > > > > > > options as well as a positive indication to the user that an option is > > > > > > used. > > > > > > > > > > > > An example VF token option would take this form: > > > > > > > > > > > > "0000:03:00.0 vf_token=2ab74924-c335-45f4-9b16-8569e5b08258" > > > > > > > > > > > > When accessing a VF where the PF is making use of vfio-pci, the user > > > > > > MUST provide the current vf_token. When accessing a PF, the user > > MUST > > > > > > provide the current vf_token IF there are active VF users or MAY > > provide > > > > > > a vf_token in order to set the current VF token when no VF users are > > > > > > active. The former requirement assures VF users that an > > unassociated > > > > > > driver cannot usurp the PF device. These semantics also imply that a > > > > > > VF token MUST be set by a PF driver before VF drivers can access their > > > > > > device, the default token is random and mechanisms to read the > > token > > > > are > > > > > > not provided in order to protect the VF token of previous users. Use > > of > > > > > > the vf_token option outside of these cases will return an error, as > > > > > > discussed above. > > > > > > > > > > > > Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx> > > > > > > --- > > > > > > drivers/vfio/pci/vfio_pci.c | 198 > > > > > > +++++++++++++++++++++++++++++++++++ > > > > > > drivers/vfio/pci/vfio_pci_private.h | 8 + > > > > > > 2 files changed, 205 insertions(+), 1 deletion(-) > > > > > > > > > > > > diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c > > > > > > index 2ec6c31d0ab0..8dd6ef9543ca 100644 > > > > > > --- a/drivers/vfio/pci/vfio_pci.c > > > > > > +++ b/drivers/vfio/pci/vfio_pci.c > > > > > > @@ -466,6 +466,44 @@ static void vfio_pci_disable(struct > > > > vfio_pci_device > > > > > > *vdev) > > > > > > vfio_pci_set_power_state(vdev, PCI_D3hot); > > > > > > } > > > > > > > > > > > > +static struct pci_driver vfio_pci_driver; > > > > > > + > > > > > > +static struct vfio_pci_device *get_pf_vdev(struct vfio_pci_device > > *vdev, > > > > > > + struct vfio_device **pf_dev) > > > > > > +{ > > > > > > + struct pci_dev *physfn = pci_physfn(vdev->pdev); > > > > > > + > > > > > > + if (!vdev->pdev->is_virtfn) > > > > > > + return NULL; > > > > > > + > > > > > > + *pf_dev = vfio_device_get_from_dev(&physfn->dev); > > > > > > + if (!*pf_dev) > > > > > > + return NULL; > > > > > > + > > > > > > + if (pci_dev_driver(physfn) != &vfio_pci_driver) { > > > > > > + vfio_device_put(*pf_dev); > > > > > > + return NULL; > > > > > > + } > > > > > > + > > > > > > + return vfio_device_data(*pf_dev); > > > > > > +} > > > > > > + > > > > > > +static void vfio_pci_vf_token_user_add(struct vfio_pci_device *vdev, > > int > > > > val) > > > > > > +{ > > > > > > + struct vfio_device *pf_dev; > > > > > > + struct vfio_pci_device *pf_vdev = get_pf_vdev(vdev, > > &pf_dev); > > > > > > + > > > > > > + if (!pf_vdev) > > > > > > + return; > > > > > > + > > > > > > + mutex_lock(&pf_vdev->vf_token->lock); > > > > > > + pf_vdev->vf_token->users += val; > > > > > > + WARN_ON(pf_vdev->vf_token->users < 0); > > > > > > + mutex_unlock(&pf_vdev->vf_token->lock); > > > > > > + > > > > > > + vfio_device_put(pf_dev); > > > > > > +} > > > > > > + > > > > > > static void vfio_pci_release(void *device_data) > > > > > > { > > > > > > struct vfio_pci_device *vdev = device_data; > > > > > > @@ -473,6 +511,7 @@ static void vfio_pci_release(void *device_data) > > > > > > mutex_lock(&vdev->reflck->lock); > > > > > > > > > > > > if (!(--vdev->refcnt)) { > > > > > > + vfio_pci_vf_token_user_add(vdev, -1); > > > > > > vfio_spapr_pci_eeh_release(vdev->pdev); > > > > > > vfio_pci_disable(vdev); > > > > > > } > > > > > > @@ -498,6 +537,7 @@ static int vfio_pci_open(void *device_data) > > > > > > goto error; > > > > > > > > > > > > vfio_spapr_pci_eeh_open(vdev->pdev); > > > > > > + vfio_pci_vf_token_user_add(vdev, 1); > > > > > > } > > > > > > vdev->refcnt++; > > > > > > error: > > > > > > @@ -1278,11 +1318,148 @@ static void vfio_pci_request(void > > > > *device_data, > > > > > > unsigned int count) > > > > > > mutex_unlock(&vdev->igate); > > > > > > } > > > > > > > > > > > > +static int vfio_pci_validate_vf_token(struct vfio_pci_device *vdev, > > > > > > + bool vf_token, uuid_t *uuid) > > > > > > +{ > > > > > > + /* > > > > > > + * There's always some degree of trust or collaboration > > between SR- > > > > > > IOV > > > > > > + * PF and VFs, even if just that the PF hosts the SR-IOV > > capability and > > > > > > + * can disrupt VFs with a reset, but often the PF has more > > explicit > > > > > > + * access to deny service to the VF or access data passed > > through the > > > > > > + * VF. We therefore require an opt-in via a shared VF token > > (UUID) > > > > > > to > > > > > > + * represent this trust. This both prevents that a VF driver > > might > > > > > > + * assume the PF driver is a trusted, in-kernel driver, and also > > that > > > > > > + * a PF driver might be replaced with a rogue driver, unknown > > to in- > > > > > > use > > > > > > + * VF drivers. > > > > > > + * > > > > > > + * Therefore when presented with a VF, if the PF is a vfio > > device and > > > > > > + * it is bound to the vfio-pci driver, the user needs to provide > > a VF > > > > > > + * token to access the device, in the form of appending a > > vf_token to > > > > > > + * the device name, for example: > > > > > > + * > > > > > > + * "0000:04:10.0 vf_token=bd8d9d2b-5a5f-4f5a-a211- > > f591514ba1f3" > > > > > > + * > > > > > > + * When presented with a PF which has VFs in use, the user > > must also > > > > > > + * provide the current VF token to prove collaboration with > > existing > > > > > > + * VF users. If VFs are not in use, the VF token provided for > > the PF > > > > > > + * device will act to set the VF token. > > > > > > + * > > > > > > + * If the VF token is provided but unused, a fault is generated. > > > > > > > > > > fault->error, otherwise it is easy to consider a CPU fault. 😊 > > > > > > > > Ok, I can make that change, but I think you might have a unique > > > > background to make a leap that a userspace ioctl can trigger a CPU > > > > fault ;) > > > > > > > > > > + */ > > > > > > + if (!vdev->pdev->is_virtfn && !vdev->vf_token && !vf_token) > > > > > > + return 0; /* No VF token provided or required */ > > > > > > + > > > > > > + if (vdev->pdev->is_virtfn) { > > > > > > + struct vfio_device *pf_dev; > > > > > > + struct vfio_pci_device *pf_vdev = get_pf_vdev(vdev, > > > > > > &pf_dev); > > > > > > + bool match; > > > > > > + > > > > > > + if (!pf_vdev) { > > > > > > + if (!vf_token) > > > > > > + return 0; /* PF is not vfio-pci, no VF > > token */ > > > > > > + > > > > > > + pci_info_ratelimited(vdev->pdev, > > > > > > + "VF token incorrectly provided, PF not > > bound > > > > > > to vfio-pci\n"); > > > > > > + return -EINVAL; > > > > > > + } > > > > > > + > > > > > > + if (!vf_token) { > > > > > > + vfio_device_put(pf_dev); > > > > > > + pci_info_ratelimited(vdev->pdev, > > > > > > + "VF token required to access > > device\n"); > > > > > > + return -EACCES; > > > > > > + } > > > > > > + > > > > > > + mutex_lock(&pf_vdev->vf_token->lock); > > > > > > + match = uuid_equal(uuid, &pf_vdev->vf_token- > > >uuid); > > > > > > + mutex_unlock(&pf_vdev->vf_token->lock); > > > > > > + > > > > > > + vfio_device_put(pf_dev); > > > > > > + > > > > > > + if (!match) { > > > > > > + pci_info_ratelimited(vdev->pdev, > > > > > > + "Incorrect VF token provided for > > device\n"); > > > > > > + return -EACCES; > > > > > > + } > > > > > > + } else if (vdev->vf_token) { > > > > > > + mutex_lock(&vdev->vf_token->lock); > > > > > > + if (vdev->vf_token->users) { > > > > > > + if (!vf_token) { > > > > > > + mutex_unlock(&vdev->vf_token- > > >lock); > > > > > > + pci_info_ratelimited(vdev->pdev, > > > > > > + "VF token required to access > > > > > > device\n"); > > > > > > + return -EACCES; > > > > > > + } > > > > > > + > > > > > > + if (!uuid_equal(uuid, &vdev->vf_token->uuid)) > > { > > > > > > + mutex_unlock(&vdev->vf_token- > > >lock); > > > > > > + pci_info_ratelimited(vdev->pdev, > > > > > > + "Incorrect VF token provided > > for > > > > > > device\n"); > > > > > > + return -EACCES; > > > > > > + } > > > > > > + } else if (vf_token) { > > > > > > + uuid_copy(&vdev->vf_token->uuid, uuid); > > > > > > + } > > > > > > > > > > It implies that we allow PF to be accessed w/o providing a VF token, > > > > > as long as no VF is currently in-use, which further means no VF can > > > > > be further assigned since no one knows the random uuid allocated > > > > > by vfio. Just want to confirm whether it is the desired flavor. If an > > > > > user really wants to use PF-only, possibly he should disable SR-IOV > > > > > instead... > > > > > > > > Yes, this is the behavior I'm intending. Are you suggesting that we > > > > should require a VF token in order to access a PF that has SR-IOV > > > > already enabled? This introduces an inconsistency that SR-IOV can be > > > > > > yes. I felt that it's meaningless otherwise if an user has no attempt to > > > manage SR-IOV but still leaving it enabled. In many cases, enabling of > > > SR-IOV may reserve some resource in the hardware, thus simply hurting > > > PF performance. > > > > But a user needs to be granted access to a device by a privileged > > entity and the privileged entity may also enable SR-IOV, so it seems > > you're assuming the privileged entity is operating independently and > > not in the best interest of enabling the specific user case. > > what about throwing out a warning for such situation? so the userspace > knows some collaboration is missing before its access to the device. This seems arbitrary. pci-pf-stub proves to us that there are devices that need no special setup for SR-IOV, we don't know that we don't have such a device. Enabling SR-IOV after the user opens the device also doesn't indicate there's necessarily collaboration between the two, so if we generate a warning on one, how do we assume the other is ok? I don't really understand why this is generating such concern. Thanks, Alex > > > > enabled via sysfs asynchronous to the GET_DEVICE_FD ioctl, so we'd > > need > > > > to secure the sysfs interface to only allow enabling SR-IOV when the PF > > > > is already opened to cases where the VF token is already set? Thus > > > > > > yes, the PF is assigned to the userspace driver, thus it's reasonable to > > > have the userspace driver decide whether to enable or disable SR-IOV > > > when the PF is under its control. as I replied to patch [5/7], the sysfs > > > interface alone looks problematic w/o knowing whether the userspace > > > driver is willing to manage VFs (by setting a token)... > > > > As I replied in patch [5/7] the operations don't need to happen > > independently, configuring SR-IOV in advance of the user driver > > attaching or in collaboration with the user driver can also be enabled > > with this series as is. Allowing the user driver to directly enable > > SR-IOV and create VFs in the host is something I've avoided here, but > > not precluded for later extensions. I think that allowing a user to > > perform these operations represents a degree of privilege beyond > > ownership of the PF itself, which is why I'm currently only enabling > > the sysfs sriov_configure interface. The user driver needs to work in > > collaboration with a privileged entity to enable SR-IOV, or be granted > > access to operate on the sysfs interface directly. > > Thanks. this assumption was clearly overlooked in my previous thinking. > > > > > > > SR-IOV could be pre-enabled, but the user must provide a vf_token > > > > option on GET_DEVICE_FD, otherwise SR-IOV could only be enabled after > > > > the user sets a VF token. But then do we need to invalidate the token > > > > at some point, or else it seems like we have the same scenario when the > > > > next user comes along. We believe there are PFs that require no > > > > > > I think so, e.g. when SR-IOV is being disabled, or when the fd is closed. > > > > Can you articulate a specific risk that this would resolve? If we have > > devices like the one supported by pci-pf-stub, where it's apparently > > sufficient to provide no device access other than to enable SR-IOV on > > the PF, re-implementing that in vfio-pci would require that the > > userspace driver is notified when the SR-IOV configuration is changed > > such that a VF token can be re-inserted. For what gain? > > > > > > special VF support other than sriov_configure, so those driver could > > > > theoretically close the PF after setting a VF token. That makes it > > > > > > theoretically yes, but I'm not sure the real gain of supporting such > > > usage. 😊 > > > > Likewise I don't see the gain of restricting it. > > > > > btw with your question I realize another potential open. Now an > > > user could also use sysfs to reset the PF, which definitely affects the > > > state of VFs. Do we want a token match with that path? or such > > > intention is assumed to be trusted by VF drivers given that only > > > privileged users can do it? > > > > I think we're going into the weeds here, a privileged user can use the > > pci-sysfs reset interface to break all sorts of things. I'm certainly > > not going to propose any sort of VF token interface to restrict it. > > Privileged users can do bad things via sysfs. Privileged users can > > configure PFs in ways that may not be compatible with any given > > userspace VF driver. I'm assuming collaboration in the best interest > > of enabling the user driver. Thanks, > > > > Alex > > > > > > difficult to determine the lifetime of a VF token and leads to the > > > > interface proposed here of an initial random token, then the user set > > > > token persisting indefinitely. > > > > > > > > I've tended consider all of these to be mechanisms that a user can > > > > shoot themselves in the foot. Yes, the user and admin can do things > > > > that will fail to work with this interface, for example my testing > > > > involves QEMU, where we don't expose SR-IOV to the guest yet and the > > > > igb driver for the PF will encounter problems running a device with > > > > SR-IOV enabled that it doesn't know about. Do we want to try to play > > > > nanny and require specific semantics? I've opt'd for the more simple > > > > code here. > > > > > > > > > > + > > > > > > + mutex_unlock(&vdev->vf_token->lock); > > > > > > + } else if (vf_token) { > > > > > > + pci_info_ratelimited(vdev->pdev, > > > > > > + "VF token incorrectly provided, not a PF or > > VF\n"); > > > > > > + return -EINVAL; > > > > > > + } > > > > > > + > > > > > > + return 0; > > > > > > +} > > > > > > + > > > > > > +#define VF_TOKEN_ARG "vf_token=" > > > > > > + > > > > > > static int vfio_pci_match(void *device_data, char *buf) > > > > > > { > > > > > > struct vfio_pci_device *vdev = device_data; > > > > > > + bool vf_token = false; > > > > > > + uuid_t uuid; > > > > > > + int ret; > > > > > > + > > > > > > + if (strncmp(pci_name(vdev->pdev), buf, > > strlen(pci_name(vdev- > > > > > > >pdev)))) > > > > > > + return 0; /* No match */ > > > > > > + > > > > > > + if (strlen(buf) > strlen(pci_name(vdev->pdev))) { > > > > > > + buf += strlen(pci_name(vdev->pdev)); > > > > > > + > > > > > > + if (*buf != ' ') > > > > > > + return 0; /* No match: non-whitespace after > > name */ > > > > > > + > > > > > > + while (*buf) { > > > > > > + if (*buf == ' ') { > > > > > > + buf++; > > > > > > + continue; > > > > > > + } > > > > > > + > > > > > > + if (!vf_token && !strncmp(buf, > > VF_TOKEN_ARG, > > > > > > + > > strlen(VF_TOKEN_ARG))) { > > > > > > + buf += strlen(VF_TOKEN_ARG); > > > > > > + > > > > > > + if (strlen(buf) < UUID_STRING_LEN) > > > > > > + return -EINVAL; > > > > > > + > > > > > > + ret = uuid_parse(buf, &uuid); > > > > > > + if (ret) > > > > > > + return ret; > > > > > > > > > > > > - return !strcmp(pci_name(vdev->pdev), buf); > > > > > > + vf_token = true; > > > > > > + buf += UUID_STRING_LEN; > > > > > > + } else { > > > > > > + /* Unknown/duplicate option */ > > > > > > + return -EINVAL; > > > > > > + } > > > > > > + } > > > > > > + } > > > > > > + > > > > > > + ret = vfio_pci_validate_vf_token(vdev, vf_token, &uuid); > > > > > > + if (ret) > > > > > > + return ret; > > > > > > + > > > > > > + return 1; /* Match */ > > > > > > } > > > > > > > > > > > > static const struct vfio_device_ops vfio_pci_ops = { > > > > > > @@ -1354,6 +1531,19 @@ static int vfio_pci_probe(struct pci_dev > > *pdev, > > > > > > const struct pci_device_id *id) > > > > > > return ret; > > > > > > } > > > > > > > > > > > > + if (pdev->is_physfn) { > > > > > > + vdev->vf_token = kzalloc(sizeof(*vdev->vf_token), > > > > > > GFP_KERNEL); > > > > > > + if (!vdev->vf_token) { > > > > > > + vfio_pci_reflck_put(vdev->reflck); > > > > > > + vfio_del_group_dev(&pdev->dev); > > > > > > + vfio_iommu_group_put(group, &pdev->dev); > > > > > > + kfree(vdev); > > > > > > + return -ENOMEM; > > > > > > + } > > > > > > + mutex_init(&vdev->vf_token->lock); > > > > > > + uuid_gen(&vdev->vf_token->uuid); > > > > > > > > > > should we also regenerate a random uuid somewhere when SR-IOV is > > > > > disabled and then re-enabled on a PF? Although vfio disallows > > userspace > > > > > to read uuid, it is always safer to avoid caching a secret from previous > > > > > user. > > > > > > > > What if our user is QEMU emulating SR-IOV to the guest. Do we want to > > > > force a new VF token is set every time we bounce the VFs? Why? As > > > > above, the session lifetime of the VF token might be difficult to > > > > determine and I'm not sure paranoia is a sufficient reason to try to > > > > create boundaries for it. Thanks, > > > > > > > > Alex > > > > > > > > > > + } > > > > > > + > > > > > > if (vfio_pci_is_vga(pdev)) { > > > > > > vga_client_register(pdev, vdev, NULL, > > > > > > vfio_pci_set_vga_decode); > > > > > > vga_set_legacy_decoding(pdev, > > > > > > @@ -1387,6 +1577,12 @@ static void vfio_pci_remove(struct pci_dev > > > > *pdev) > > > > > > if (!vdev) > > > > > > return; > > > > > > > > > > > > + if (vdev->vf_token) { > > > > > > + WARN_ON(vdev->vf_token->users); > > > > > > + mutex_destroy(&vdev->vf_token->lock); > > > > > > + kfree(vdev->vf_token); > > > > > > + } > > > > > > + > > > > > > vfio_pci_reflck_put(vdev->reflck); > > > > > > > > > > > > vfio_iommu_group_put(pdev->dev.iommu_group, &pdev->dev); > > > > > > diff --git a/drivers/vfio/pci/vfio_pci_private.h > > > > > > b/drivers/vfio/pci/vfio_pci_private.h > > > > > > index 8a2c7607d513..76c11c915949 100644 > > > > > > --- a/drivers/vfio/pci/vfio_pci_private.h > > > > > > +++ b/drivers/vfio/pci/vfio_pci_private.h > > > > > > @@ -12,6 +12,7 @@ > > > > > > #include <linux/pci.h> > > > > > > #include <linux/irqbypass.h> > > > > > > #include <linux/types.h> > > > > > > +#include <linux/uuid.h> > > > > > > > > > > > > #ifndef VFIO_PCI_PRIVATE_H > > > > > > #define VFIO_PCI_PRIVATE_H > > > > > > @@ -84,6 +85,12 @@ struct vfio_pci_reflck { > > > > > > struct mutex lock; > > > > > > }; > > > > > > > > > > > > +struct vfio_pci_vf_token { > > > > > > + struct mutex lock; > > > > > > + uuid_t uuid; > > > > > > + int users; > > > > > > +}; > > > > > > + > > > > > > struct vfio_pci_device { > > > > > > struct pci_dev *pdev; > > > > > > void __iomem *barmap[PCI_STD_NUM_BARS]; > > > > > > @@ -122,6 +129,7 @@ struct vfio_pci_device { > > > > > > struct list_head dummy_resources_list; > > > > > > struct mutex ioeventfds_lock; > > > > > > struct list_head ioeventfds_list; > > > > > > + struct vfio_pci_vf_token *vf_token; > > > > > > }; > > > > > > > > > > > > #define is_intx(vdev) (vdev->irq_type == VFIO_PCI_INTX_IRQ_INDEX) > > > > > > > > >