From: Arnd Bergmann arnd@arndb.de
commit 7b53cca764f9b291b7907fcd39d9e66ad728ee0b upstream.
As seen from a recent syzbot bug report, mistakes in the compat ioctl implementation can lead to uninitialized kernel stack data getting used as input for driver ioctl handlers.
The reported bug is now fixed, but it's possible that other related bugs are still present or get added in the future. As the drivers need to check user input already, the possible impact is fairly low, but it might still cause an information leak.
To be on the safe side, always clear the entire ioctl buffer before calling the conversion handler functions that are meant to initialize them.
Signed-off-by: Arnd Bergmann arnd@arndb.de Reviewed-by: Laurent Pinchart laurent.pinchart@ideasonboard.com Signed-off-by: Hans Verkuil hverkuil-cisco@xs4all.nl Signed-off-by: Mauro Carvalho Chehab mchehab+huawei@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/media/v4l2-core/v4l2-ioctl.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/drivers/media/v4l2-core/v4l2-ioctl.c +++ b/drivers/media/v4l2-core/v4l2-ioctl.c @@ -3124,8 +3124,10 @@ static int video_get_user(void __user *a if (copy_from_user(parg, (void __user *)arg, n)) err = -EFAULT; } else if (in_compat_syscall()) { + memset(parg, 0, n); err = v4l2_compat_get_user(arg, parg, cmd); } else { + memset(parg, 0, n); #if !defined(CONFIG_64BIT) && defined(CONFIG_COMPAT_32BIT_TIME) switch (cmd) { case VIDIOC_QUERYBUF_TIME32: