media: v4l2-ctrls-api: fix error handling for v4l2_g_ctrl()

As detected by Coverity, 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@vger.kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

diff --git a/drivers/media/v4l2-core/v4l2-ctrls-api.c b/drivers/media/v4l2-core/v4l2-ctrls-api.c
index e5a364e..95a2202 100644 (file)
--- 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);
@@ -811,10 +815,11 @@ static int set_ctrl_lock(struct v4l2_fh *fh, struct v4l2_ctrl *ctrl,
        int ret;
 
        v4l2_ctrl_lock(ctrl);
-       user_to_new(c, ctrl);
-       ret = set_ctrl(fh, ctrl, 0);
+       ret = user_to_new(c, ctrl);
+       if (!ret)
+               ret = set_ctrl(fh, ctrl, 0);
        if (!ret)
-               cur_to_user(c, ctrl);
+               ret = cur_to_user(c, ctrl);
        v4l2_ctrl_unlock(ctrl);
        return ret;
 }