From: Johan Hovold <johan@kernel.org>
Date: Mon, 26 Apr 2021 08:11:49 +0000 (+0200)
Subject: net: hso: fix NULL-deref on disconnect regression
X-Git-Tag: v4.9.268~1
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=0c71d4c89559f72cec2592d078681a843bce570e;p=thirdparty%2Fkernel%2Fstable.git

net: hso: fix NULL-deref on disconnect regression

commit 2ad5692db72874f02b9ad551d26345437ea4f7f3 upstream.

Commit 8a12f8836145 ("net: hso: fix null-ptr-deref during tty device
unregistration") fixed the racy minor allocation reported by syzbot, but
introduced an unconditional NULL-pointer dereference on every disconnect
instead.

Specifically, the serial device table must no longer be accessed after
the minor has been released by hso_serial_tty_unregister().

Fixes: 8a12f8836145 ("net: hso: fix null-ptr-deref during tty device unregistration")
Cc: stable@vger.kernel.org
Cc: Anirudh Rayabharam <mail@anirudhrb.com>
Reported-by: Leonardo Antoniazzi <leoanto@aruba.it>
Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Anirudh Rayabharam <mail@anirudhrb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
index e3123d49e5d85..6ecccc737974c 100644
--- a/drivers/net/usb/hso.c
+++ b/drivers/net/usb/hso.c
@@ -3115,7 +3115,7 @@ static void hso_free_interface(struct usb_interface *interface)
 			cancel_work_sync(&serial_table[i]->async_put_intf);
 			cancel_work_sync(&serial_table[i]->async_get_intf);
 			hso_serial_tty_unregister(serial);
-			kref_put(&serial_table[i]->ref, hso_serial_ref_free);
+			kref_put(&serial->parent->ref, hso_serial_ref_free);
 		}
 	}