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iommu/vt-d: Fix general protection fault in aux_detach_device()
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The aux-domain attach/detach are not tracked, some data structures might
be used after free. This causes general protection faults when multiple
subdevices are created and assigned to a same guest machine:

  | general protection fault, probably for non-canonical address 0xdead000000000100: 0000 [#1] SMP NOPTI
  | RIP: 0010:intel_iommu_aux_detach_device+0x12a/0x1f0
  | [...]
  | Call Trace:
  |  iommu_aux_detach_device+0x24/0x70
  |  vfio_mdev_detach_domain+0x3b/0x60
  |  ? vfio_mdev_set_domain+0x50/0x50
  |  iommu_group_for_each_dev+0x4f/0x80
  |  vfio_iommu_detach_group.isra.0+0x22/0x30
  |  vfio_iommu_type1_detach_group.cold+0x71/0x211
  |  ? find_exported_symbol_in_section+0x4a/0xd0
  |  ? each_symbol_section+0x28/0x50
  |  __vfio_group_unset_container+0x4d/0x150
  |  vfio_group_try_dissolve_container+0x25/0x30
  |  vfio_group_put_external_user+0x13/0x20
  |  kvm_vfio_group_put_external_user+0x27/0x40 [kvm]
  |  kvm_vfio_destroy+0x45/0xb0 [kvm]
  |  kvm_put_kvm+0x1bb/0x2e0 [kvm]
  |  kvm_vm_release+0x22/0x30 [kvm]
  |  __fput+0xcc/0x260
  |  ____fput+0xe/0x10
  |  task_work_run+0x8f/0xb0
  |  do_exit+0x358/0xaf0
  |  ? wake_up_state+0x10/0x20
  |  ? signal_wake_up_state+0x1a/0x30
  |  do_group_exit+0x47/0xb0
  |  __x64_sys_exit_group+0x18/0x20
  |  do_syscall_64+0x57/0x1d0
  |  entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fix the crash by tracking the subdevices when attaching and detaching
aux-domains.

Fixes: 67b8e02 ("iommu/vt-d: Aux-domain specific domain attach/detach")
Co-developed-by: Xin Zeng <xin.zeng@intel.com>
Signed-off-by: Xin Zeng <xin.zeng@intel.com>
Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
Acked-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/1609949037-25291-3-git-send-email-yi.l.liu@intel.com
Signed-off-by: Will Deacon <will@kernel.org>
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@yiliu1765 @willdeacon
yiliu1765 authored and willdeacon committed Jan 7, 2021
1 parent 9ad9f45 commit 18abda7
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Showing 2 changed files with 82 additions and 29 deletions.
95 changes: 71 additions & 24 deletions drivers/iommu/intel/iommu.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1877,6 +1877,7 @@ static struct dmar_domain *alloc_domain(int flags)
domain->flags |= DOMAIN_FLAG_USE_FIRST_LEVEL;
domain->has_iotlb_device = false;
INIT_LIST_HEAD(&domain->devices);
INIT_LIST_HEAD(&domain->subdevices);

return domain;
}
Expand Down Expand Up @@ -2547,7 +2548,7 @@ static struct dmar_domain *dmar_insert_one_dev_info(struct intel_iommu *iommu,
info->iommu = iommu;
info->pasid_table = NULL;
info->auxd_enabled = 0;
INIT_LIST_HEAD(&info->auxiliary_domains);
INIT_LIST_HEAD(&info->subdevices);

if (dev && dev_is_pci(dev)) {
struct pci_dev *pdev = to_pci_dev(info->dev);
Expand Down Expand Up @@ -4475,33 +4476,61 @@ is_aux_domain(struct device *dev, struct iommu_domain *domain)
domain->type == IOMMU_DOMAIN_UNMANAGED;
}

static void auxiliary_link_device(struct dmar_domain *domain,
struct device *dev)
static inline struct subdev_domain_info *
lookup_subdev_info(struct dmar_domain *domain, struct device *dev)
{
struct subdev_domain_info *sinfo;

if (!list_empty(&domain->subdevices)) {
list_for_each_entry(sinfo, &domain->subdevices, link_domain) {
if (sinfo->pdev == dev)
return sinfo;
}
}

return NULL;
}

static int auxiliary_link_device(struct dmar_domain *domain,
struct device *dev)
{
struct device_domain_info *info = get_domain_info(dev);
struct subdev_domain_info *sinfo = lookup_subdev_info(domain, dev);

assert_spin_locked(&device_domain_lock);
if (WARN_ON(!info))
return;
return -EINVAL;

if (!sinfo) {
sinfo = kzalloc(sizeof(*sinfo), GFP_ATOMIC);
sinfo->domain = domain;
sinfo->pdev = dev;
list_add(&sinfo->link_phys, &info->subdevices);
list_add(&sinfo->link_domain, &domain->subdevices);
}

domain->auxd_refcnt++;
list_add(&domain->auxd, &info->auxiliary_domains);
return ++sinfo->users;
}

static void auxiliary_unlink_device(struct dmar_domain *domain,
struct device *dev)
static int auxiliary_unlink_device(struct dmar_domain *domain,
struct device *dev)
{
struct device_domain_info *info = get_domain_info(dev);
struct subdev_domain_info *sinfo = lookup_subdev_info(domain, dev);
int ret;

assert_spin_locked(&device_domain_lock);
if (WARN_ON(!info))
return;
if (WARN_ON(!info || !sinfo || sinfo->users <= 0))
return -EINVAL;

list_del(&domain->auxd);
domain->auxd_refcnt--;
ret = --sinfo->users;
if (!ret) {
list_del(&sinfo->link_phys);
list_del(&sinfo->link_domain);
kfree(sinfo);
}

if (!domain->auxd_refcnt && domain->default_pasid > 0)
ioasid_put(domain->default_pasid);
return ret;
}

static int aux_domain_add_dev(struct dmar_domain *domain,
Expand Down Expand Up @@ -4530,6 +4559,19 @@ static int aux_domain_add_dev(struct dmar_domain *domain,
}

spin_lock_irqsave(&device_domain_lock, flags);
ret = auxiliary_link_device(domain, dev);
if (ret <= 0)
goto link_failed;

/*
* Subdevices from the same physical device can be attached to the
* same domain. For such cases, only the first subdevice attachment
* needs to go through the full steps in this function. So if ret >
* 1, just goto out.
*/
if (ret > 1)
goto out;

/*
* iommu->lock must be held to attach domain to iommu and setup the
* pasid entry for second level translation.
Expand All @@ -4548,10 +4590,9 @@ static int aux_domain_add_dev(struct dmar_domain *domain,
domain->default_pasid);
if (ret)
goto table_failed;
spin_unlock(&iommu->lock);

auxiliary_link_device(domain, dev);

spin_unlock(&iommu->lock);
out:
spin_unlock_irqrestore(&device_domain_lock, flags);

return 0;
Expand All @@ -4560,8 +4601,10 @@ static int aux_domain_add_dev(struct dmar_domain *domain,
domain_detach_iommu(domain, iommu);
attach_failed:
spin_unlock(&iommu->lock);
auxiliary_unlink_device(domain, dev);
link_failed:
spin_unlock_irqrestore(&device_domain_lock, flags);
if (!domain->auxd_refcnt && domain->default_pasid > 0)
if (list_empty(&domain->subdevices) && domain->default_pasid > 0)
ioasid_put(domain->default_pasid);

return ret;
Expand All @@ -4581,14 +4624,18 @@ static void aux_domain_remove_dev(struct dmar_domain *domain,
info = get_domain_info(dev);
iommu = info->iommu;

auxiliary_unlink_device(domain, dev);

spin_lock(&iommu->lock);
intel_pasid_tear_down_entry(iommu, dev, domain->default_pasid, false);
domain_detach_iommu(domain, iommu);
spin_unlock(&iommu->lock);
if (!auxiliary_unlink_device(domain, dev)) {
spin_lock(&iommu->lock);
intel_pasid_tear_down_entry(iommu, dev,
domain->default_pasid, false);
domain_detach_iommu(domain, iommu);
spin_unlock(&iommu->lock);
}

spin_unlock_irqrestore(&device_domain_lock, flags);

if (list_empty(&domain->subdevices) && domain->default_pasid > 0)
ioasid_put(domain->default_pasid);
}

static int prepare_domain_attach_device(struct iommu_domain *domain,
Expand Down
16 changes: 11 additions & 5 deletions include/linux/intel-iommu.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -533,11 +533,10 @@ struct dmar_domain {
/* Domain ids per IOMMU. Use u16 since
* domain ids are 16 bit wide according
* to VT-d spec, section 9.3 */
unsigned int auxd_refcnt; /* Refcount of auxiliary attaching */

bool has_iotlb_device;
struct list_head devices; /* all devices' list */
struct list_head auxd; /* link to device's auxiliary list */
struct list_head subdevices; /* all subdevices' list */
struct iova_domain iovad; /* iova's that belong to this domain */

struct dma_pte *pgd; /* virtual address */
Expand Down Expand Up @@ -610,14 +609,21 @@ struct intel_iommu {
struct dmar_drhd_unit *drhd;
};

/* Per subdevice private data */
struct subdev_domain_info {
struct list_head link_phys; /* link to phys device siblings */
struct list_head link_domain; /* link to domain siblings */
struct device *pdev; /* physical device derived from */
struct dmar_domain *domain; /* aux-domain */
int users; /* user count */
};

/* PCI domain-device relationship */
struct device_domain_info {
struct list_head link; /* link to domain siblings */
struct list_head global; /* link to global list */
struct list_head table; /* link to pasid table */
struct list_head auxiliary_domains; /* auxiliary domains
* attached to this device
*/
struct list_head subdevices; /* subdevices sibling */
u32 segment; /* PCI segment number */
u8 bus; /* PCI bus number */
u8 devfn; /* PCI devfn number */
Expand Down

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