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media: rc: uevent sysfs file races with rc_unregister_device() 

Only report uevent file contents if device still registered, else we
might read freed memory.

Reported-by: syzbot+ceef16277388d6f24898@syzkaller.appspotmail.com
Cc: Hillf Danton <hdanton@sina.com>
Cc: <stable@vger.kernel.org> # 4.16+
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
This commit is contained in:
Sean Young 2020-08-08 13:19:12 +02:00 committed by Mauro Carvalho Chehab
parent 8a30c017c9
commit 4f0835d667
1 changed files with 16 additions and 16 deletions
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32
drivers/media/rc/rc-main.c
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@ -1601,25 +1601,25 @@ static void rc_dev_release(struct device *device)
kfree(dev);
}
#define ADD_HOTPLUG_VAR(fmt, val...) \
do { \
int err = add_uevent_var(env, fmt, val); \
if (err) \
return err; \
} while (0)
static int rc_dev_uevent(struct device *device, struct kobj_uevent_env *env)
{
struct rc_dev *dev = to_rc_dev(device);
int ret = 0;
if (dev->rc_map.name)
ADD_HOTPLUG_VAR("NAME=%s", dev->rc_map.name);
if (dev->driver_name)
ADD_HOTPLUG_VAR("DRV_NAME=%s", dev->driver_name);
if (dev->device_name)
ADD_HOTPLUG_VAR("DEV_NAME=%s", dev->device_name);
mutex_lock(&dev->lock);
return 0;
if (!dev->registered)
ret = -ENODEV;
if (ret == 0 && dev->rc_map.name)
ret = add_uevent_var(env, "NAME=%s", dev->rc_map.name);
if (ret == 0 && dev->driver_name)
ret = add_uevent_var(env, "DRV_NAME=%s", dev->driver_name);
if (ret == 0 && dev->device_name)
ret = add_uevent_var(env, "DEV_NAME=%s", dev->device_name);
mutex_unlock(&dev->lock);
return ret;
}
/*
@ -2011,14 +2011,14 @@ void rc_unregister_device(struct rc_dev *dev)
del_timer_sync(&dev->timer_keyup);
del_timer_sync(&dev->timer_repeat);
rc_free_rx_device(dev);
mutex_lock(&dev->lock);
if (dev->users && dev->close)
dev->close(dev);
dev->registered = false;
mutex_unlock(&dev->lock);
rc_free_rx_device(dev);
/*
* lirc device should be freed with dev->registered = false, so
* that userspace polling will get notified.