Author: ian
Date: Fri Jan 13 16:37:38 2017
New Revision: 312077
URL: https://svnweb.freebsd.org/changeset/base/312077
Log:
Check tty_gone() after allocating IO buffers. The tty lock has to be
dropped then reacquired due to using M_WAITOK, which opens a window in
which the tty device can disappear. Check for this and return ENXIO
back up the call chain so that callers can cope.
This closes a race where TF_GONE would get set while buffers were being
allocated as part of ttydev_open(), causing a subsequent call to
ttydevsw_modem() later in ttydev_open() to assert.
Reported by: pho
Reviewed by: kib
Modified:
head/sys/kern/tty.c
head/sys/kern/tty_inq.c
head/sys/kern/tty_outq.c
head/sys/sys/ttyqueue.h
Modified: head/sys/kern/tty.c
==============================================================================
--- head/sys/kern/tty.c Fri Jan 13 15:17:25 2017 (r312076)
+++ head/sys/kern/tty.c Fri Jan 13 16:37:38 2017 (r312077)
@@ -105,25 +105,38 @@ SYSCTL_INT(_kern, OID_AUTO, tty_drainwai
#define TTYBUF_MAX 65536
-static void
+/*
+ * Allocate buffer space if necessary, and set low watermarks, based on speed.
+ * Note that the ttyxxxq_setsize() functions may drop and then reacquire the
tty
+ * lock during memory allocation. They will return ENXIO if the tty disappears
+ * while unlocked.
+ */
+static int
tty_watermarks(struct tty *tp)
{
size_t bs = 0;
+ int error;
/* Provide an input buffer for 0.2 seconds of data. */
if (tp->t_termios.c_cflag & CREAD)
bs = MIN(tp->t_termios.c_ispeed / 5, TTYBUF_MAX);
- ttyinq_setsize(&tp->t_inq, tp, bs);
+ error = ttyinq_setsize(&tp->t_inq, tp, bs);
+ if (error != 0)
+ return (error);
/* Set low watermark at 10% (when 90% is available). */
tp->t_inlow = (ttyinq_getallocatedsize(&tp->t_inq) * 9) / 10;
/* Provide an output buffer for 0.2 seconds of data. */
bs = MIN(tp->t_termios.c_ospeed / 5, TTYBUF_MAX);
- ttyoutq_setsize(&tp->t_outq, tp, bs);
+ error = ttyoutq_setsize(&tp->t_outq, tp, bs);
+ if (error != 0)
+ return (error);
/* Set low watermark at 10% (when 90% is available). */
tp->t_outlow = (ttyoutq_getallocatedsize(&tp->t_outq) * 9) / 10;
+
+ return (0);
}
static int
@@ -318,7 +331,9 @@ ttydev_open(struct cdev *dev, int oflags
goto done;
ttydisc_open(tp);
- tty_watermarks(tp); /* XXXGL: drops lock */
+ error = tty_watermarks(tp);
+ if (error != 0)
+ goto done;
}
/* Wait for Carrier Detect. */
@@ -1627,7 +1642,9 @@ tty_generic_ioctl(struct tty *tp, u_long
tp->t_termios.c_ospeed = t->c_ospeed;
/* Baud rate has changed - update watermarks. */
- tty_watermarks(tp);
+ error = tty_watermarks(tp);
+ if (error)
+ return (error);
}
/* Copy new non-device driver parameters. */
Modified: head/sys/kern/tty_inq.c
==============================================================================
--- head/sys/kern/tty_inq.c Fri Jan 13 15:17:25 2017 (r312076)
+++ head/sys/kern/tty_inq.c Fri Jan 13 16:37:38 2017 (r312077)
@@ -112,7 +112,7 @@ static uma_zone_t ttyinq_zone;
TTYINQ_INSERT_TAIL(ti, tib); \
} while (0)
-void
+int
ttyinq_setsize(struct ttyinq *ti, struct tty *tp, size_t size)
{
struct ttyinq_block *tib;
@@ -134,8 +134,14 @@ ttyinq_setsize(struct ttyinq *ti, struct
tib = uma_zalloc(ttyinq_zone, M_WAITOK);
tty_lock(tp);
+ if (tty_gone(tp)) {
+ uma_zfree(ttyinq_zone, tib);
+ return (ENXIO);
+ }
+
TTYINQ_INSERT_TAIL(ti, tib);
}
+ return (0);
}
void
Modified: head/sys/kern/tty_outq.c
==============================================================================
--- head/sys/kern/tty_outq.c Fri Jan 13 15:17:25 2017 (r312076)
+++ head/sys/kern/tty_outq.c Fri Jan 13 16:37:38 2017 (r312077)
@@ -89,7 +89,7 @@ ttyoutq_flush(struct ttyoutq *to)
to->to_end = 0;
}
-void
+int
ttyoutq_setsize(struct ttyoutq *to, struct tty *tp, size_t size)
{
struct ttyoutq_block *tob;
@@ -111,8 +111,14 @@ ttyoutq_setsize(struct ttyoutq *to, stru
tob = uma_zalloc(ttyoutq_zone, M_WAITOK);
tty_lock(tp);
+ if (tty_gone(tp)) {
+ uma_zfree(ttyoutq_zone, tob);
+ return (ENXIO);
+ }
+
TTYOUTQ_INSERT_TAIL(to, tob);
}
+ return (0);
}
void
Modified: head/sys/sys/ttyqueue.h
==============================================================================
--- head/sys/sys/ttyqueue.h Fri Jan 13 15:17:25 2017 (r312076)
+++ head/sys/sys/ttyqueue.h Fri Jan 13 16:37:38 2017 (r312077)
@@ -69,7 +69,7 @@ struct ttyoutq {
#ifdef _KERNEL
/* Input queue handling routines. */
-void ttyinq_setsize(struct ttyinq *ti, struct tty *tp, size_t len);
+int ttyinq_setsize(struct ttyinq *ti, struct tty *tp, size_t len);
void ttyinq_free(struct ttyinq *ti);
int ttyinq_read_uio(struct ttyinq *ti, struct tty *tp, struct uio *uio,
size_t readlen, size_t flushlen);
@@ -136,7 +136,7 @@ void ttyinq_line_iterate_from_reprintpos
/* Output queue handling routines. */
void ttyoutq_flush(struct ttyoutq *to);
-void ttyoutq_setsize(struct ttyoutq *to, struct tty *tp, size_t len);
+int ttyoutq_setsize(struct ttyoutq *to, struct tty *tp, size_t len);
void ttyoutq_free(struct ttyoutq *to);
size_t ttyoutq_read(struct ttyoutq *to, void *buf, size_t len);
int ttyoutq_read_uio(struct ttyoutq *to, struct tty *tp, struct uio *uio);
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