linux-stable.git/drivers/xen, branch v4.4.2

Merge tag 'for-linus-4.4-rc5-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

2015-12-18T20:24:52+00:00

Pull xen bug fixes from David Vrabel:
 - XSA-155 security fixes to backend drivers.
 - XSA-157 security fixes to pciback.

* tag 'for-linus-4.4-rc5-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen-pciback: fix up cleanup path when alloc fails
  xen/pciback: Don't allow MSI-X ops if PCI_COMMAND_MEMORY is not set.
  xen/pciback: For XEN_PCI_OP_disable_msi[|x] only disable if device has MSI(X) enabled.
  xen/pciback: Do not install an IRQ handler for MSI interrupts.
  xen/pciback: Return error on XEN_PCI_OP_enable_msix when device has MSI or MSI-X enabled
  xen/pciback: Return error on XEN_PCI_OP_enable_msi when device has MSI or MSI-X enabled
  xen/pciback: Save xen_pci_op commands before processing it
  xen-scsiback: safely copy requests
  xen-blkback: read from indirect descriptors only once
  xen-blkback: only read request operation from shared ring once
  xen-netback: use RING_COPY_REQUEST() throughout
  xen-netback: don't use last request to determine minimum Tx credit
  xen: Add RING_COPY_REQUEST()
  xen/x86/pvh: Use HVM's flush_tlb_others op
  xen: Resume PMU from non-atomic context
  xen/events/fifo: Consume unprocessed events when a CPU dies

xen-pciback: fix up cleanup path when alloc fails

2015-12-18T16:38:48+00:00

When allocating a pciback device fails, clear the private
field. This could lead to an use-after free, however
the 'really_probe' takes care of setting
dev_set_drvdata(dev, NULL) in its failure path (which we would
exercise if the ->probe function failed), so we we
are OK. However lets be defensive as the code can change.

Going forward we should clean up the pci_set_drvdata(dev, NULL)
in the various code-base. That will be for another day.

Reviewed-by: Boris Ostrovsky 
Reported-by: Jonathan Creekmore 
Signed-off-by: Doug Goldstein 
Signed-off-by: Konrad Rzeszutek Wilk

xen/pciback: Don't allow MSI-X ops if PCI_COMMAND_MEMORY is not set.

2015-12-18T15:48:39+00:00

commit f598282f51 ("PCI: Fix the NIU MSI-X problem in a better way")
teaches us that dealing with MSI-X can be troublesome.

Further checks in the MSI-X architecture shows that if the
PCI_COMMAND_MEMORY bit is turned of in the PCI_COMMAND we
may not be able to access the BAR (since they are memory regions).

Since the MSI-X tables are located in there.. that can lead
to us causing PCIe errors. Inhibit us performing any
operation on the MSI-X unless the MEMORY bit is set.

Note that Xen hypervisor with:
"x86/MSI-X: access MSI-X table only after having enabled MSI-X"
will return:
xen_pciback: 0000:0a:00.1: error -6 enabling MSI-X for guest 3!

When the generic MSI code tries to setup the PIRQ without
MEMORY bit set. Which means with later versions of Xen
(4.6) this patch is not neccessary.

This is part of XSA-157

CC: stable@vger.kernel.org
Reviewed-by: Jan Beulich 
Signed-off-by: Konrad Rzeszutek Wilk

xen/pciback: For XEN_PCI_OP_disable_msi[|x] only disable if device has MSI(X) enabled.

2015-12-18T15:48:37+00:00

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

CC: stable@vger.kernel.org
Reviewed-by: David Vrabel 
Signed-off-by: Konrad Rzeszutek Wilk

xen/pciback: Do not install an IRQ handler for MSI interrupts.

2015-12-18T15:48:34+00:00

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

CC: stable@vger.kernel.org
Reviewed-by: David Vrabel 
Signed-off-by: Konrad Rzeszutek Wilk

xen/pciback: Return error on XEN_PCI_OP_enable_msix when device has MSI or MSI-X enabled

2015-12-18T15:48:29+00:00

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

CC: stable@vger.kernel.org
Reviewed-by: David Vrabel 
Reviewed-by: Jan Beulich 
Signed-off-by: Konrad Rzeszutek Wilk

xen/pciback: Return error on XEN_PCI_OP_enable_msi when device has MSI or MSI-X enabled

2015-12-18T15:48:19+00:00

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.

CC: stable@vger.kernel.org
Reviewed-by: David Vrabel 
Reviewed-by: Jan Beulich 
Signed-off-by: Konrad Rzeszutek Wilk

xen/pciback: Save xen_pci_op commands before processing it

2015-12-18T15:00:47+00:00

Double fetch vulnerabilities that happen when a variable is
fetched twice from shared memory but a security check is only
performed the first time.

The xen_pcibk_do_op function performs a switch statements on the op->cmd
value which is stored in shared memory. Interestingly this can result
in a double fetch vulnerability depending on the performed compiler
optimization.

This patch fixes it by saving the xen_pci_op command before
processing it. We also use 'barrier' to make sure that the
compiler does not perform any optimization.

This is part of XSA155.

CC: stable@vger.kernel.org
Reviewed-by: Konrad Rzeszutek Wilk 
Signed-off-by: Jan Beulich 
Signed-off-by: David Vrabel 
Signed-off-by: Konrad Rzeszutek Wilk

xen-scsiback: safely copy requests

2015-12-18T15:00:41+00:00

The copy of the ring request was lacking a following barrier(),
potentially allowing the compiler to optimize the copy away.

Use RING_COPY_REQUEST() to ensure the request is copied to local
memory.

This is part of XSA155.

CC: stable@vger.kernel.org
Reviewed-by: Juergen Gross 
Signed-off-by: David Vrabel 
Signed-off-by: Konrad Rzeszutek Wilk

xen/events/fifo: Consume unprocessed events when a CPU dies

2015-12-02T13:23:25+00:00

When a CPU is offlined, there may be unprocessed events on a port for
that CPU.  If the port is subsequently reused on a different CPU, it
could be in an unexpected state with the link bit set, resulting in
interrupts being missed. Fix this by consuming any unprocessed events
for a particular CPU when that CPU dies.

Signed-off-by: Ross Lagerwall 
Cc:  # 3.14+
Signed-off-by: David Vrabel