[PATCH 01/13] media: v4l2-ctrls-api: fix error handling for v4l2_g_ctrl()

[Mauro Carvalho Chehab]

The error check logic at get_ctrl() is broken: if ptr_to_user()
fails to fill a control due to an error, no errors are returned
and v4l2_g_ctrl() returns success on a failed operation, which
may cause applications to fail.

Add an error check at get_ctrl() and ensure that it will
be returned to userspace without filling the control value if
get_ctrl() fails.

Fixes: 71c689dc2e73 ("media: v4l2-ctrls: split up into four source files")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>
---
 drivers/media/v4l2-core/v4l2-ctrls-api.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-ctrls-api.c b/drivers/media/v4l2-core/v4l2-ctrls-api.c
index e5a364efd5e6..be32dccf9830 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls-api.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls-api.c
@@ -753,9 +753,10 @@ static int get_ctrl(struct v4l2_ctrl *ctrl, struct v4l2_ext_control *c)
 		for (i = 0; i < master->ncontrols; i++)
 			cur_to_new(master->cluster[i]);
 		ret = call_op(master, g_volatile_ctrl);
-		new_to_user(c, ctrl);
+		if (!ret)
+			ret = new_to_user(c, ctrl);
 	} else {
-		cur_to_user(c, ctrl);
+		ret = cur_to_user(c, ctrl);
 	}
 	v4l2_ctrl_unlock(master);
 	return ret;
@@ -770,7 +771,10 @@ int v4l2_g_ctrl(struct v4l2_ctrl_handler *hdl, struct v4l2_control *control)
 	if (!ctrl || !ctrl->is_int)
 		return -EINVAL;
 	ret = get_ctrl(ctrl, &c);
-	control->value = c.value;
+
+	if (!ret)
+		control->value = c.value;
+
 	return ret;
 }
 EXPORT_SYMBOL(v4l2_g_ctrl);
-- 
2.47.0