1. 16 Mar, 2016 4 commits
    • Konrad Rzeszutek Wilk's avatar
      xen/pciback: For XEN_PCI_OP_disable_msi[|x] only disable if device has MSI(X) enabled. · 388a8005
      Konrad Rzeszutek Wilk authored
      commit 7cfb905b upstream.
      
      Otherwise just continue on, returning the same values as
      previously (return of 0, and op->result has the PIRQ value).
      
      This does not change the behavior of XEN_PCI_OP_disable_msi[|x].
      
      The pci_disable_msi or pci_disable_msix have the checks for
      msi_enabled or msix_enabled so they will error out immediately.
      
      However the guest can still call these operations and cause
      us to disable the 'ack_intr'. That means the backend IRQ handler
      for the legacy interrupt will not respond to interrupts anymore.
      
      This will lead to (if the device is causing an interrupt storm)
      for the Linux generic code to disable the interrupt line.
      
      Naturally this will only happen if the device in question
      is plugged in on the motherboard on shared level interrupt GSI.
      
      This is part of XSA-157
      Reviewed-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
      Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
      388a8005
    • Konrad Rzeszutek Wilk's avatar
      xen/pciback: Do not install an IRQ handler for MSI interrupts. · 4113b288
      Konrad Rzeszutek Wilk authored
      commit a396f3a2 upstream.
      
      Otherwise an guest can subvert the generic MSI code to trigger
      an BUG_ON condition during MSI interrupt freeing:
      
       for (i = 0; i < entry->nvec_used; i++)
              BUG_ON(irq_has_action(entry->irq + i));
      
      Xen PCI backed installs an IRQ handler (request_irq) for
      the dev->irq whenever the guest writes PCI_COMMAND_MEMORY
      (or PCI_COMMAND_IO) to the PCI_COMMAND register. This is
      done in case the device has legacy interrupts the GSI line
      is shared by the backend devices.
      
      To subvert the backend the guest needs to make the backend
      to change the dev->irq from the GSI to the MSI interrupt line,
      make the backend allocate an interrupt handler, and then command
      the backend to free the MSI interrupt and hit the BUG_ON.
      
      Since the backend only calls 'request_irq' when the guest
      writes to the PCI_COMMAND register the guest needs to call
      XEN_PCI_OP_enable_msi before any other operation. This will
      cause the generic MSI code to setup an MSI entry and
      populate dev->irq with the new PIRQ value.
      
      Then the guest can write to PCI_COMMAND PCI_COMMAND_MEMORY
      and cause the backend to setup an IRQ handler for dev->irq
      (which instead of the GSI value has the MSI pirq). See
      'xen_pcibk_control_isr'.
      
      Then the guest disables the MSI: XEN_PCI_OP_disable_msi
      which ends up triggering the BUG_ON condition in 'free_msi_irqs'
      as there is an IRQ handler for the entry->irq (dev->irq).
      
      Note that this cannot be done using MSI-X as the generic
      code does not over-write dev->irq with the MSI-X PIRQ values.
      
      The patch inhibits setting up the IRQ handler if MSI or
      MSI-X (for symmetry reasons) code had been called successfully.
      
      P.S.
      Xen PCIBack when it sets up the device for the guest consumption
      ends up writting 0 to the PCI_COMMAND (see xen_pcibk_reset_device).
      XSA-120 addendum patch removed that - however when upstreaming said
      addendum we found that it caused issues with qemu upstream. That
      has now been fixed in qemu upstream.
      
      This is part of XSA-157
      Reviewed-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
      Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
      4113b288
    • Konrad Rzeszutek Wilk's avatar
      xen/pciback: Return error on XEN_PCI_OP_enable_msix when device has MSI or MSI-X enabled · d8e0a80d
      Konrad Rzeszutek Wilk authored
      commit 5e0ce145 upstream.
      
      The guest sequence of:
      
        a) XEN_PCI_OP_enable_msix
        b) XEN_PCI_OP_enable_msix
      
      results in hitting an NULL pointer due to using freed pointers.
      
      The device passed in the guest MUST have MSI-X capability.
      
      The a) constructs and SysFS representation of MSI and MSI groups.
      The b) adds a second set of them but adding in to SysFS fails (duplicate entry).
      'populate_msi_sysfs' frees the newly allocated msi_irq_groups (note that
      in a) pdev->msi_irq_groups is still set) and also free's ALL of the
      MSI-X entries of the device (the ones allocated in step a) and b)).
      
      The unwind code: 'free_msi_irqs' deletes all the entries and tries to
      delete the pdev->msi_irq_groups (which hasn't been set to NULL).
      However the pointers in the SysFS are already freed and we hit an
      NULL pointer further on when 'strlen' is attempted on a freed pointer.
      
      The patch adds a simple check in the XEN_PCI_OP_enable_msix to guard
      against that. The check for msi_enabled is not stricly neccessary.
      
      This is part of XSA-157
      Reviewed-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
      Reviewed-by: default avatarJan Beulich <jbeulich@suse.com>
      Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
      d8e0a80d
    • Konrad Rzeszutek Wilk's avatar
      xen/pciback: Return error on XEN_PCI_OP_enable_msi when device has MSI or MSI-X enabled · 0842f7d8
      Konrad Rzeszutek Wilk authored
      commit 56441f3c upstream.
      
      The guest sequence of:
      
       a) XEN_PCI_OP_enable_msi
       b) XEN_PCI_OP_enable_msi
       c) XEN_PCI_OP_disable_msi
      
      results in hitting an BUG_ON condition in the msi.c code.
      
      The MSI code uses an dev->msi_list to which it adds MSI entries.
      Under the above conditions an BUG_ON() can be hit. The device
      passed in the guest MUST have MSI capability.
      
      The a) adds the entry to the dev->msi_list and sets msi_enabled.
      The b) adds a second entry but adding in to SysFS fails (duplicate entry)
      and deletes all of the entries from msi_list and returns (with msi_enabled
      is still set).  c) pci_disable_msi passes the msi_enabled checks and hits:
      
      BUG_ON(list_empty(dev_to_msi_list(&dev->dev)));
      
      and blows up.
      
      The patch adds a simple check in the XEN_PCI_OP_enable_msi to guard
      against that. The check for msix_enabled is not stricly neccessary.
      
      This is part of XSA-157.
      Reviewed-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
      Reviewed-by: default avatarJan Beulich <jbeulich@suse.com>
      Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
      0842f7d8
  2. 14 Mar, 2016 22 commits
  3. 07 Mar, 2016 14 commits