From: Dmitry Safonov <dima@arista.com>
To: linux-kernel@vger.kernel.org
Cc: "Dmitry Safonov" <0x7f454c46@gmail.com>,
"Dmitry Safonov" <dima@arista.com>,
"Daniel Axtens" <dja@axtens.net>,
"Dmitry Vyukov" <dvyukov@google.com>,
"Michael Neuling" <mikey@neuling.org>,
"Mikulas Patocka" <mpatocka@redhat.com>,
"Nathan March" <nathan@gt.net>, "Pasi Kärkkäinen" <pasik@iki.fi>,
"Peter Hurley" <peter@hurleysoftware.com>,
"Sergey Senozhatsky" <sergey.senozhatsky.work@gmail.com>,
"Tan Xiaojun" <tanxiaojun@huawei.com>,
"Tetsuo Handa" <penguin-kernel@I-love.SAKURA.ne.jp>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Jiri Slaby" <jslaby@suse.com>
Subject: [PATCHv2 3/4] tty/lockdep: Add ldisc_sem asserts
Date: Mon, 3 Sep 2018 17:52:56 +0100 [thread overview]
Message-ID: <20180903165257.29227-4-dima@arista.com> (raw)
In-Reply-To: <20180903165257.29227-1-dima@arista.com>
Make sure under CONFIG_LOCKDEP that each change to line discipline
is done with held write semaphor.
Otherwise potential reader will have a good time dereferencing
incomplete/uninitialized ldisc.
Exception here is tty_ldisc_open(), as it's called without ldisc_sem
locked by tty_init_dev() for the tty->link.
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
drivers/tty/tty_ldisc.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index fc4c97cae01e..202cb645582f 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -471,6 +471,7 @@ static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
{
+ lockdep_assert_held(&tty->ldisc_sem);
WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags));
clear_bit(TTY_LDISC_OPEN, &tty->flags);
if (ld->ops->close)
@@ -492,6 +493,7 @@ static int tty_ldisc_failto(struct tty_struct *tty, int ld)
struct tty_ldisc *disc = tty_ldisc_get(tty, ld);
int r;
+ lockdep_assert_held(&tty->ldisc_sem);
if (IS_ERR(disc))
return PTR_ERR(disc);
tty->ldisc = disc;
@@ -615,6 +617,7 @@ EXPORT_SYMBOL_GPL(tty_set_ldisc);
*/
static void tty_ldisc_kill(struct tty_struct *tty)
{
+ lockdep_assert_held(&tty->ldisc_sem);
if (!tty->ldisc)
return;
/*
@@ -662,6 +665,7 @@ int tty_ldisc_reinit(struct tty_struct *tty, int disc)
struct tty_ldisc *ld;
int retval;
+ lockdep_assert_held(&tty->ldisc_sem);
ld = tty_ldisc_get(tty, disc);
if (IS_ERR(ld)) {
BUG_ON(disc == N_TTY);
@@ -825,6 +829,7 @@ int tty_ldisc_init(struct tty_struct *tty)
*/
void tty_ldisc_deinit(struct tty_struct *tty)
{
+ /* no ldisc_sem, tty is being destroyed */
if (tty->ldisc)
tty_ldisc_put(tty->ldisc);
tty->ldisc = NULL;
--
2.13.6
next prev parent reply other threads:[~2018-09-03 16:53 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-03 16:52 [PATCHv2 0/4] tty: Hold write ldisc sem in tty_reopen() Dmitry Safonov
2018-09-03 16:52 ` [PATCHv2 1/4] tty: Drop tty->count on tty_reopen() failure Dmitry Safonov
2018-09-04 8:58 ` Jiri Slaby
2018-09-03 16:52 ` [PATCHv2 2/4] tty: Hold tty_ldisc_lock() during tty_reopen() Dmitry Safonov
2018-09-04 1:51 ` Sergey Senozhatsky
2018-09-04 6:30 ` Jiri Slaby
2018-09-04 7:06 ` Sergey Senozhatsky
2018-09-04 9:02 ` Jiri Slaby
2018-09-03 16:52 ` Dmitry Safonov [this message]
2018-09-03 16:52 ` [PATCHv2 4/4] tty: Simplify tty->count math in tty_reopen() Dmitry Safonov
2018-09-04 9:03 ` Jiri Slaby
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