linux-kernel - [PATCH 2/2] vfio/fsl-mc: prevent underflow in vfio_fsl_mc

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Date:   Fri, 23 Oct 2020 14:29:47 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Diana Craciun <diana.craciun@....nxp.com>
Cc:     Alex Williamson <alex.williamson@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH 2/2] vfio/fsl-mc: prevent underflow in vfio_fsl_mc_mmap()

My static analsysis tool complains that the "index" can be negative.
There are some checks in do_mmap() which try to prevent underflows but
I don't know if they are sufficient for this situation.  Either way,
making "index" unsigned is harmless so let's do it just to be safe.

Fixes: 67247289688d ("vfio/fsl-mc: Allow userspace to MMAP fsl-mc device MMIO regions")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
 drivers/vfio/fsl-mc/vfio_fsl_mc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vfio/fsl-mc/vfio_fsl_mc.c b/drivers/vfio/fsl-mc/vfio_fsl_mc.c
index 21f22e3da11f..f27e25112c40 100644
--- a/drivers/vfio/fsl-mc/vfio_fsl_mc.c
+++ b/drivers/vfio/fsl-mc/vfio_fsl_mc.c
@@ -472,7 +472,7 @@ static int vfio_fsl_mc_mmap(void *device_data, struct vm_area_struct *vma)
 {
 	struct vfio_fsl_mc_device *vdev = device_data;
 	struct fsl_mc_device *mc_dev = vdev->mc_dev;
-	int index;
+	unsigned int index;
 
 	index = vma->vm_pgoff >> (VFIO_FSL_MC_OFFSET_SHIFT - PAGE_SHIFT);
 
-- 
2.28.0