[PATCH 4.9 091/175] media: saa7146: fix array overflow in vidioc_s_audio()

[Greg Kroah-Hartman]

From: Dan Carpenter <dan.carpen...@oracle.com>

[ Upstream commit 8e4d86e241cf035d6d3467cd346e7ce490681937 ]

The "a->index" value comes from the user via the ioctl.  The problem is
that the shift can wrap resulting in setting "mxb->cur_audinput" to an
invalid value, which later results in an array overflow.

Fixes: 6680427791c9 ("[media] mxb: fix audio handling")
Signed-off-by: Dan Carpenter <dan.carpen...@oracle.com>
Signed-off-by: Hans Verkuil <hverkuil-ci...@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+hua...@kernel.org>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 drivers/media/pci/saa7146/mxb.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/media/pci/saa7146/mxb.c b/drivers/media/pci/saa7146/mxb.c
index 504d788076392..3e8753c9e1e47 100644
--- a/drivers/media/pci/saa7146/mxb.c
+++ b/drivers/media/pci/saa7146/mxb.c
@@ -652,16 +652,17 @@ static int vidioc_s_audio(struct file *file, void *fh, 
const struct v4l2_audio *
        struct mxb *mxb = (struct mxb *)dev->ext_priv;
 
        DEB_D("VIDIOC_S_AUDIO %d\n", a->index);
-       if (mxb_inputs[mxb->cur_input].audioset & (1 << a->index)) {
-               if (mxb->cur_audinput != a->index) {
-                       mxb->cur_audinput = a->index;
-                       tea6420_route(mxb, a->index);
-                       if (mxb->cur_audinput == 0)
-                               mxb_update_audmode(mxb);
-               }
-               return 0;
+       if (a->index >= 32 ||
+           !(mxb_inputs[mxb->cur_input].audioset & (1 << a->index)))
+               return -EINVAL;
+
+       if (mxb->cur_audinput != a->index) {
+               mxb->cur_audinput = a->index;
+               tea6420_route(mxb, a->index);
+               if (mxb->cur_audinput == 0)
+                       mxb_update_audmode(mxb);
        }
-       return -EINVAL;
+       return 0;
 }
 
 #ifdef CONFIG_VIDEO_ADV_DEBUG
-- 
2.27.0