[PATCH v3] vfio/pci: Fix integer overflows, bitmask check

[Vlad Tsyrklevich <vlad@tsyrklevich.net>]

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>
---
 drivers/vfio/pci/vfio_pci.c       | 33 +++++++++++++++++++++------------
 drivers/vfio/pci/vfio_pci_intrs.c |  2 +-
 2 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index d624a52..031bc08 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -829,8 +829,9 @@ static long vfio_pci_ioctl(void *device_data,
 
 	} 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);
 
@@ -838,23 +839,31 @@ static long vfio_pci_ioctl(void *device_data,
 			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);
+		max = vfio_pci_get_irq_count(vdev, hdr.index);
+		if (hdr.start >= max || hdr.start + hdr.count > max)
+			return -EINVAL;
 
-			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;
+		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),
diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
index c2e6089..1c46045 100644
--- a/drivers/vfio/pci/vfio_pci_intrs.c
+++ b/drivers/vfio/pci/vfio_pci_intrs.c
@@ -256,7 +256,7 @@ static int vfio_msi_enable(struct vfio_pci_device *vdev, int nvec, bool msix)
 	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;
 
-- 
2.7.0