[Linux-kernel-mentees] [PATCH v2] vivid: Fix global-out-of-bounds read in precalculate_color()

[Peilin Ye]

vivid_meta_out_process() is setting `brightness`, `contrast`, `saturation`
and `hue` using tpg_s_*(). This is wrong, since tpg_s_*() do not provide
range checks. Using tpg_s_*() here also makes the control framework
out-of-sync with the actual values. Use v4l2_ctrl_s_ctrl() instead.

This issue has been reported by syzbot as an out-of-bounds read bug in
precalculate_color().

Fixes: 746facd39370 ("media: vivid: Add metadata output support")
Reported-and-tested-by: syzbot+02d9172bf4c43104cd70@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://syzkaller.appspot.com/bug?extid=02d9172bf4c43104cd70
Suggested-by: Hans Verkuil <hverkuil@xxxxxxxxx>
Signed-off-by: Peilin Ye <yepeilin.cs@xxxxxxxxx>
---
I'm not very sure how to name this patch since we are fixing a bug in
v4l2-tpg by modifying vivid.

Change in v2:
    - Solve the root of the problem instead of adding more boundary checks
      in precalculate_color(). (Suggested by Hans Verkuil
      <hverkuil@xxxxxxxxx>)

 drivers/media/test-drivers/vivid/vivid-meta-out.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/media/test-drivers/vivid/vivid-meta-out.c b/drivers/media/test-drivers/vivid/vivid-meta-out.c
index ff8a039aba72..95835b52b58f 100644
--- a/drivers/media/test-drivers/vivid/vivid-meta-out.c
+++ b/drivers/media/test-drivers/vivid/vivid-meta-out.c
@@ -164,10 +164,11 @@ void vivid_meta_out_process(struct vivid_dev *dev,
 {
 	struct vivid_meta_out_buf *meta = vb2_plane_vaddr(&buf->vb.vb2_buf, 0);
 
-	tpg_s_brightness(&dev->tpg, meta->brightness);
-	tpg_s_contrast(&dev->tpg, meta->contrast);
-	tpg_s_saturation(&dev->tpg, meta->saturation);
-	tpg_s_hue(&dev->tpg, meta->hue);
+	v4l2_ctrl_s_ctrl(dev->brightness, meta->brightness);
+	v4l2_ctrl_s_ctrl(dev->contrast, meta->contrast);
+	v4l2_ctrl_s_ctrl(dev->saturation, meta->saturation);
+	v4l2_ctrl_s_ctrl(dev->hue, meta->hue);
+
 	dprintk(dev, 2, " %s brightness %u contrast %u saturation %u hue %d\n",
 		__func__, meta->brightness, meta->contrast,
 		meta->saturation, meta->hue);
-- 
2.25.1