linux-kernel - [PATCH] vfio/pci: Fix unsigned comparison overflow

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Message-ID: <20160201235430.21791.64530.stgit@gimli.home>
Date:	Mon, 01 Feb 2016 16:54:49 -0700
From:	Alex Williamson <alex.williamson@...hat.com>
To:	alex.williamson@...hat.com
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	eric.auger@...aro.org
Subject: [PATCH] vfio/pci: Fix unsigned comparison overflow

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@...aro.org>
Signed-off-by: Alex Williamson <alex.williamson@...hat.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);
 	}