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

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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 <david.vrabel@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Konrad Rzeszutek Wilk 2015-04-03 11:08:22 -04:00
parent 8135cf8b09
commit 56441f3c8e
1 changed files with 6 additions and 1 deletions
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7
drivers/xen/xen-pciback/pciback_ops.c
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@ -144,7 +144,12 @@ int xen_pcibk_enable_msi(struct xen_pcibk_device *pdev,
if (unlikely(verbose_request))
printk(KERN_DEBUG DRV_NAME ": %s: enable MSI\n", pci_name(dev));
status = pci_enable_msi(dev);
if (dev->msi_enabled)
status = -EALREADY;
else if (dev->msix_enabled)
status = -ENXIO;
else
status = pci_enable_msi(dev);
if (status) {
pr_warn_ratelimited("%s: error enabling MSI for guest %u: err %d\n",