media: v4l2-core: only zero-out ioctl-read buffers

The memset() got moved out of the check for _IOC_NONE, so passing a
made-up command number with a size but no direction would allow clearing
data on user-provided pointers.

Move video_get_user() back into the _IOC_NONE check where it belongs.

Reported-by: syzbot+54fd8cca4b7226c94b8e@syzkaller.appspotmail.com
Fixes: 6c625c01c7a6 ("media: v4l2-core: split out data copy from video_usercopy")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
index b68ff06..aaf83e2 100644 (file)
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -3205,12 +3205,12 @@ video_usercopy(struct file *file, unsigned int orig_cmd, unsigned long arg,
                        parg = mbuf;
                }
 
+               err = video_get_user((void __user *)arg, parg, orig_cmd,
+                                    &always_copy);
+               if (err)
+                       goto out;
        }
 
-       err = video_get_user((void __user *)arg, parg, orig_cmd, &always_copy);
-       if (err)
-               goto out;
-
        err = check_array_args(cmd, parg, &array_size, &user_ptr, &kernel_ptr);
        if (err < 0)
                goto out;