[PATCH] vfio/pci: Fix unsigned comparison overflow

Alex Williamson
2016-02-01T23:54:49Z

Signed versus unsigned comparisons are implicitly cast to unsigned,
which result in a couple possible overflows. For instance (start +
count) might overflow and wrap, getting through our validation test.
Also when unwinding setup, -1 being compared as unsigned doesn't
produce the intended stop condition. Fix both of these and also fix
vfio_msi_set_vector_signal() to validate parameters before using the
vector index, though none of the callers should pass bad indexes
anymore.

Reported-by: Eric Auger <eric.auger@linaro.org>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
drivers/vfio/pci/vfio_pci_intrs.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
index 3b3ba15..e9ea3fe 100644
--- a/drivers/vfio/pci/vfio_pci_intrs.c
+++ b/drivers/vfio/pci/vfio_pci_intrs.c
@@ -309,14 +309,14 @@ static int vfio_msi_set_vector_signal(struct vfio_pci_device *vdev,
int vector, int fd, bool msix)
{
struct pci_dev *pdev = vdev->pdev;
- int irq = msix ? vdev->msix[vector].vector : pdev->irq + vector;
- char *name = msix ? "vfio-msix" : "vfio-msi";
struct eventfd_ctx *trigger;
- int ret;
+ int irq, ret;

- if (vector >= vdev->num_ctx)
+ if (vector < 0 || vector >= vdev->num_ctx)
return -EINVAL;

+ irq = msix ? vdev->msix[vector].vector : pdev->irq + vector;
+
if (vdev->ctx[vector].trigger) {
free_irq(irq, vdev->ctx[vector].trigger);
irq_bypass_unregister_producer(&vdev->ctx[vector].producer);
@@ -328,8 +328,9 @@ static int vfio_msi_set_vector_signal(struct vfio_pci_device *vdev,
if (fd < 0)
return 0;

- vdev->ctx[vector].name = kasprintf(GFP_KERNEL, "%s[%d](%s)",
- name, vector, pci_name(pdev));
+ vdev->ctx[vector].name = kasprintf(GFP_KERNEL, "vfio-msi%s[%d](%s)",
+ msix ? "x" : "", vector,
+ pci_name(pdev));
if (!vdev->ctx[vector].name)
return -ENOMEM;

@@ -379,7 +380,7 @@ static int vfio_msi_set_block(struct vfio_pci_device *vdev, unsigned start,
{
int i, j, ret = 0;

- if (start + count > vdev->num_ctx)
+ if (start >= vdev->num_ctx || start + count > vdev->num_ctx)
return -EINVAL;

for (i = 0, j = start; i < count && !ret; i++, j++) {
@@ -388,7 +389,7 @@ static int vfio_msi_set_block(struct vfio_pci_device *vdev, unsigned start,
}

if (ret) {
- for (--j; j >= start; j--)
+ for (--j; j >= (int)start; j--)
vfio_msi_set_vector_signal(vdev, j, -1, msix);
}