[PATCH 3.18 45/47] vfio/pci: Fix integer overflows, bitmask check

Greg Kroah-Hartman
2017-04-28T08:38:58Z

From: Vlad Tsyrklevich <vlad@tsyrklevich.net>

commit 05692d7005a364add85c6e25a6c4447ce08f913a upstream.

The VFIO_DEVICE_SET_IRQS ioctl did not sufficiently sanitize
user-supplied integers, potentially allowing memory corruption. This
patch adds appropriate integer overflow checks, checks the range bounds
for VFIO_IRQ_SET_DATA_NONE, and also verifies that only single element
in the VFIO_IRQ_SET_DATA_TYPE_MASK bitmask is set.
VFIO_IRQ_SET_ACTION_TYPE_MASK is already correctly checked later in
vfio_pci_set_irqs_ioctl().

Furthermore, a kzalloc is changed to a kcalloc because the use of a
kzalloc with an integer multiplication allowed an integer overflow
condition to be reached without this patch. kcalloc checks for overflow
and should prevent a similar occurrence.

Signed-off-by: Vlad Tsyrklevich <vlad@tsyrklevich.net>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Cc: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/vfio/pci/vfio_pci.c | 35 ++++++++++++++++++++++-------------
drivers/vfio/pci/vfio_pci_intrs.c | 2 +-
2 files changed, 23 insertions(+), 14 deletions(-)

--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -489,8 +489,9 @@ static long vfio_pci_ioctl(void *device_

} else if (cmd == VFIO_DEVICE_SET_IRQS) {
struct vfio_irq_set hdr;
+ size_t size;
u8 *data = NULL;
- int ret = 0;
+ int max, ret = 0;

minsz = offsetofend(struct vfio_irq_set, count);

@@ -498,23 +499,31 @@ static long vfio_pci_ioctl(void *device_
return -EFAULT;

if (hdr.argsz < minsz || hdr.index >= VFIO_PCI_NUM_IRQS ||
+ hdr.count >= (U32_MAX - hdr.start) ||
hdr.flags & ~(VFIO_IRQ_SET_DATA_TYPE_MASK |
VFIO_IRQ_SET_ACTION_TYPE_MASK))
return -EINVAL;

- if (!(hdr.flags & VFIO_IRQ_SET_DATA_NONE)) {
- size_t size;
- int max = vfio_pci_get_irq_count(vdev, hdr.index);
-
- if (hdr.flags & VFIO_IRQ_SET_DATA_BOOL)
- size = sizeof(uint8_t);
- else if (hdr.flags & VFIO_IRQ_SET_DATA_EVENTFD)
- size = sizeof(int32_t);
- else
- return -EINVAL;
+ max = vfio_pci_get_irq_count(vdev, hdr.index);
+ if (hdr.start >= max || hdr.start + hdr.count > max)
+ return -EINVAL;
+
+ switch (hdr.flags & VFIO_IRQ_SET_DATA_TYPE_MASK) {
+ case VFIO_IRQ_SET_DATA_NONE:
+ size = 0;
+ break;
+ case VFIO_IRQ_SET_DATA_BOOL:
+ size = sizeof(uint8_t);
+ break;
+ case VFIO_IRQ_SET_DATA_EVENTFD:
+ size = sizeof(int32_t);
+ break;
+ default:
+ return -EINVAL;
+ }

- if (hdr.argsz - minsz < hdr.count * size ||
- hdr.start >= max || hdr.start + hdr.count > max)
+ if (size) {
+ if (hdr.argsz - minsz < hdr.count * size)
return -EINVAL;

data = memdup_user((void __user *)(arg + minsz),
--- a/drivers/vfio/pci/vfio_pci_intrs.c
+++ b/drivers/vfio/pci/vfio_pci_intrs.c
@@ -466,7 +466,7 @@ static int vfio_msi_enable(struct vfio_p
if (!is_irq_none(vdev))
return -EINVAL;

- vdev->ctx = kzalloc(nvec * sizeof(struct vfio_pci_irq_ctx), GFP_KERNEL);
+ vdev->ctx = kcalloc(nvec, sizeof(struct vfio_pci_irq_ctx), GFP_KERNEL);
if (!vdev->ctx)
return -ENOMEM;