From bfb48b54db25c3b4ef4bef5e0691464ebc4aa335 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Mon, 14 Jun 2021 12:34:03 +0200 Subject: [PATCH] media: v4l2-core: explicitly clear ioctl input data 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 Reviewed-by: Laurent Pinchart Signed-off-by: Hans Verkuil Signed-off-by: Mauro Carvalho Chehab Signed-off-by: Greg Kroah-Hartman --- drivers/media/v4l2-core/v4l2-ioctl.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c index 07d823656ee65..cf50c60bbb5d3 100644 --- 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 *arg, void *parg, 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: