Commit 6d2c5b15 authored Jan 15, 2020 by dan.carpenter@oracle.com Committed by Greg Kroah-Hartman Mar 11, 2020

HID: hiddev: Fix race in in hiddev_disconnect()



commit 5c02c447eaeda29d3da121a2e17b97ccaf579b51 upstream.

Syzbot reports that "hiddev" is used after it's free in hiddev_disconnect().
The hiddev_disconnect() function sets "hiddev->exist = 0;" so
hiddev_release() can free it as soon as we drop the "existancelock"
lock.  This patch moves the mutex_unlock(&hiddev->existancelock) until
after we have finished using it.

Reported-by:  <syzbot+784ccb935f9900cc7c9e@syzkaller.appspotmail.com>
Fixes: 7f77897e ("HID: hiddev: fix potential use-after-free")
Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 3adb1f8c

drivers/hid/usbhid/hiddev.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -962,9 +962,9 @@ void hiddev_disconnect(struct hid_device *hid)
		hiddev->exist = 0;

		if (hiddev->open) {
		mutex_unlock(&hiddev->existancelock);
		usbhid_close(hiddev->hid);
		wake_up_interruptible(&hiddev->wait);
		mutex_unlock(&hiddev->existancelock);
		} else {
		mutex_unlock(&hiddev->existancelock);
		kfree(hiddev);