linux-kernel - [patch 2/3] vfio: make count unsigned to prevent integer underflow

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Message-ID: <20120628064458.GB11107@elgon.mountain>
Date:	Thu, 28 Jun 2012 09:44:58 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: [patch 2/3] vfio: make count unsigned to prevent integer underflow

In vfio_pci_ioctl() there is a potential integer underflow where we
might allocate less data than intended.  We check that hdr.count is not
too large, but we don't check whether it is negative:

drivers/vfio/pci/vfio_pci.c
   312          if (hdr.argsz - minsz < hdr.count * size ||
   313              hdr.count > vfio_pci_get_irq_count(vdev, hdr.index))
   314                  return -EINVAL;
   315
   316          data = kmalloc(hdr.count * size, GFP_KERNEL);

Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 300d49b..86ef2da 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -347,7 +347,7 @@ struct vfio_irq_set {
 #define VFIO_IRQ_SET_ACTION_TRIGGER	(1 << 5) /* Trigger interrupt */
 	__u32	index;
 	__s32	start;
-	__s32	count;
+	__u32	count;
 	__u8	data[];
 };
 #define VFIO_DEVICE_SET_IRQS		_IO(VFIO_TYPE, VFIO_BASE + 10)
--
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