Commit 5e0ce145 authored Nov 02, 2015 by Konrad Rzeszutek Wilk

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



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 <david.vrabel@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

parent 56441f3c

drivers/xen/xen-pciback/pciback_ops.c

+7 −0

Original line number	Original line	Diff line number	Diff line
	@@ -206,9 +206,16 @@ int xen_pcibk_enable_msix(struct xen_pcibk_device *pdev,
	if (unlikely(verbose_request))		if (unlikely(verbose_request))
	printk(KERN_DEBUG DRV_NAME ": %s: enable MSI-X\n",		printk(KERN_DEBUG DRV_NAME ": %s: enable MSI-X\n",
	pci_name(dev));		pci_name(dev));

	if (op->value > SH_INFO_MAX_VEC)		if (op->value > SH_INFO_MAX_VEC)
	return -EINVAL;		return -EINVAL;

			if (dev->msix_enabled)
			return -EALREADY;

			if (dev->msi_enabled)
			return -ENXIO;

	entries = kmalloc(op->value * sizeof(*entries), GFP_KERNEL);		entries = kmalloc(op->value * sizeof(*entries), GFP_KERNEL);
	if (entries == NULL)		if (entries == NULL)
	return -ENOMEM;		return -ENOMEM;