CVS commit: src/sys/dev/usb

[matthew green]

Module Name:    src
Committed By:   mrg
Date:           Wed May  1 06:01:01 UTC 2019

Modified Files:
        src/sys/dev/usb: ucom.c

Log Message:
fix a locking botch in ucomhwiflow():

tty.c always calls t_hwiflow() with tty_lock held, and the caller
of this for ucom always holds sc->sc_lock when calling down into
the tty layer.

don't try to re-take the sc_lock in ucomhwiflow() (locking against
myself is triggered here currently), but instead assert that the
lock is already held _and_ that tty_lock is held.

in ucom_detach(), when closing pipes set sc_bulkin_pipe and
sc_bulkout_pipe to NULL.  fixes bug noticed by code inspection:
a failed detach would attempt to close them a second time.


To generate a diff of this commit:
cvs rdiff -u -r1.122 -r1.123 src/sys/dev/usb/ucom.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.


Modified files:

Index: src/sys/dev/usb/ucom.c
diff -u src/sys/dev/usb/ucom.c:1.122 src/sys/dev/usb/ucom.c:1.123
--- src/sys/dev/usb/ucom.c:1.122	Sat Apr 20 05:53:18 2019
+++ src/sys/dev/usb/ucom.c	Wed May  1 06:01:01 2019
@@ -1,4 +1,4 @@
-/*	$NetBSD: ucom.c,v 1.122 2019/04/20 05:53:18 mrg Exp $	*/
+/*	$NetBSD: ucom.c,v 1.123 2019/05/01 06:01:01 mrg Exp $	*/
 
 /*
  * Copyright (c) 1998, 2000 The NetBSD Foundation, Inc.
@@ -34,7 +34,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ucom.c,v 1.122 2019/04/20 05:53:18 mrg Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ucom.c,v 1.123 2019/05/01 06:01:01 mrg Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_usb.h"
@@ -413,10 +413,14 @@ ucom_detach(device_t self, int flags)
 
 	pmf_device_deregister(self);
 
-	if (sc->sc_bulkin_pipe != NULL)
+	if (sc->sc_bulkin_pipe != NULL) {
 		usbd_abort_pipe(sc->sc_bulkin_pipe);
-	if (sc->sc_bulkout_pipe != NULL)
+		sc->sc_bulkin_pipe = NULL;
+	}
+	if (sc->sc_bulkout_pipe != NULL) {
 		usbd_abort_pipe(sc->sc_bulkout_pipe);
+		sc->sc_bulkout_pipe = NULL;
+	}
 
 	mutex_enter(&sc->sc_lock);
 
@@ -1263,7 +1267,9 @@ ucomhwiflow(struct tty *tp, int block)
 	if (sc == NULL)
 		return 0;
 
-	mutex_enter(&sc->sc_lock);
+	KASSERT(&sc->sc_lock);
+	KASSERT(mutex_owned(&tty_lock));
+
 	old = sc->sc_rx_stopped;
 	sc->sc_rx_stopped = (u_char)block;
 
@@ -1273,7 +1279,6 @@ ucomhwiflow(struct tty *tp, int block)
 		softint_schedule(sc->sc_si);
 		kpreempt_enable();
 	}
-	mutex_exit(&sc->sc_lock);
 
 	return 1;
 }