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authorKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2015-11-16 12:40:48 -0500
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2015-12-18 10:00:47 -0500
commit8135cf8b092723dbfcc611fe6fdcb3a36c9951c5 (patch)
treed1f03969e8a2af5ff9e2b2ea8eaab58405ac30eb /drivers/xen
parentbe69746ec12f35b484707da505c6c76ff06f97dc (diff)
downloadlinux-8135cf8b092723dbfcc611fe6fdcb3a36c9951c5.tar.bz2
xen/pciback: Save xen_pci_op commands before processing it
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 <konrad.wilk@oracle.com> Signed-off-by: Jan Beulich <JBeulich@suse.com> Signed-off-by: David Vrabel <david.vrabel@citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'drivers/xen')
-rw-r--r--drivers/xen/xen-pciback/pciback.h1
-rw-r--r--drivers/xen/xen-pciback/pciback_ops.c15
2 files changed, 15 insertions, 1 deletions
diff --git a/drivers/xen/xen-pciback/pciback.h b/drivers/xen/xen-pciback/pciback.h
index 58e38d586f52..4d529f3e40df 100644
--- a/drivers/xen/xen-pciback/pciback.h
+++ b/drivers/xen/xen-pciback/pciback.h
@@ -37,6 +37,7 @@ struct xen_pcibk_device {
struct xen_pci_sharedinfo *sh_info;
unsigned long flags;
struct work_struct op_work;
+ struct xen_pci_op op;
};
struct xen_pcibk_dev_data {
diff --git a/drivers/xen/xen-pciback/pciback_ops.c b/drivers/xen/xen-pciback/pciback_ops.c
index c4a0666de6f5..a0e0e3ed4905 100644
--- a/drivers/xen/xen-pciback/pciback_ops.c
+++ b/drivers/xen/xen-pciback/pciback_ops.c
@@ -298,9 +298,11 @@ void xen_pcibk_do_op(struct work_struct *data)
container_of(data, struct xen_pcibk_device, op_work);
struct pci_dev *dev;
struct xen_pcibk_dev_data *dev_data = NULL;
- struct xen_pci_op *op = &pdev->sh_info->op;
+ struct xen_pci_op *op = &pdev->op;
int test_intx = 0;
+ *op = pdev->sh_info->op;
+ barrier();
dev = xen_pcibk_get_pci_dev(pdev, op->domain, op->bus, op->devfn);
if (dev == NULL)
@@ -342,6 +344,17 @@ void xen_pcibk_do_op(struct work_struct *data)
if ((dev_data->enable_intx != test_intx))
xen_pcibk_control_isr(dev, 0 /* no reset */);
}
+ pdev->sh_info->op.err = op->err;
+ pdev->sh_info->op.value = op->value;
+#ifdef CONFIG_PCI_MSI
+ if (op->cmd == XEN_PCI_OP_enable_msix && op->err == 0) {
+ unsigned int i;
+
+ for (i = 0; i < op->value; i++)
+ pdev->sh_info->op.msix_entries[i].vector =
+ op->msix_entries[i].vector;
+ }
+#endif
/* Tell the driver domain that we're done. */
wmb();
clear_bit(_XEN_PCIF_active, (unsigned long *)&pdev->sh_info->flags);