[PATCH 4.13 087/109] media: Revert "[media] lirc_dev: remove superfluous get/put_device() calls"

Greg Kroah-Hartman
2017-09-24T20:43:36Z

From: Sean Young <sean@mess.org>

commit a607f51e5a4c421e2097077db88105402099c528 upstream.

This reverts commit 5be2b76a9ca4ea5fd3e221114d62eeb0d78267ca.

Only when the lirc device is freed, should we drop our reference to
rc_dev, else we the rc_dev is freed to early. If userspace has
a file descriptor open during unplug, it goes bang.

==================================================================
BUG: KASAN: use-after-free in __lock_acquire+0x7bb/0x1e10
Read of size 8 at addr ffff8801d7d61ed0 by task ir-rec/2609

-snip-
mutex_lock_nested+0x1b/0x20
? mutex_lock_nested+0x1b/0x20
rc_close.part.6+0x20/0x60 [rc_core]
rc_close+0x13/0x20 [rc_core]
lirc_dev_fop_close+0x62/0xd0 [lirc_dev]
__fput+0x236/0x410
? fput+0xb0/0xb0
? do_raw_spin_trylock+0x110/0x110
? set_rq_offline.part.70+0xa0/0xa0
____fput+0xe/0x10
task_work_run+0x116/0x180
? task_work_cancel+0x170/0x170
? _raw_spin_unlock+0x27/0x40
? switch_task_namespaces+0x5f/0x90
do_exit+0x68b/0xe80

Fixes: 5be2b76a9ca4 ("[media] lirc_dev: remove superfluous get/put_device() calls")
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/media/rc/lirc_dev.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/drivers/media/rc/lirc_dev.c
+++ b/drivers/media/rc/lirc_dev.c
@@ -59,6 +59,8 @@ static void lirc_release(struct device *
{
struct irctl *ir = container_of(ld, struct irctl, dev);

+ put_device(ir->dev.parent);
+
if (ir->buf_internal) {
lirc_buffer_free(ir->buf);
kfree(ir->buf);
@@ -218,6 +220,8 @@ int lirc_register_driver(struct lirc_dri

mutex_unlock(&lirc_dev_lock);

+ get_device(ir->dev.parent);
+
dev_info(ir->d.dev, "lirc_dev: driver %s registered at minor = %d\n",
ir->d.name, ir->d.minor);