diff options
| author | Dmitry Safonov <dima@arista.com> | 2018-11-01 00:24:51 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-12-05 12:16:33 +0100 |
| commit | 110b89282f658593a5a4a96a300d5aa51f1bf88f (patch) | |
| tree | 07c22aa906036c8799904235865098ce21f91e24 /drivers/tty | |
| parent | c18ad0cf9cb0792f448b911eb3b268a35cc6934c (diff) | |
| download | linux-110b89282f658593a5a4a96a300d5aa51f1bf88f.tar.bz2 | |
tty/ldsem: Add lockdep asserts for ldisc_sem
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.
An exception here is tty_ldisc_open(), as it's called without ldisc_sem
locked by tty_init_dev() => tty_ldisc_setup() for the tty->link.
It seem valid as tty_init_dev() will call tty_driver_install_tty()
which will find ops->install(). Install will establish tty->link in
pty_common_install(), just after allocation of slave tty with
alloc_tty_struct(). So, no one should have a reference to slave pty yet.
Cc: Jiri Slaby <jslaby@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
| -rw-r--r-- | drivers/tty/tty_ldisc.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index 9434d20cf3ca..45eda69b150c 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -478,6 +478,7 @@ 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_exclusive(&tty->ldisc_sem); WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); clear_bit(TTY_LDISC_OPEN, &tty->flags); if (ld->ops->close) @@ -499,6 +500,7 @@ 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_exclusive(&tty->ldisc_sem); if (IS_ERR(disc)) return PTR_ERR(disc); tty->ldisc = disc; @@ -622,6 +624,7 @@ EXPORT_SYMBOL_GPL(tty_set_ldisc); */ static void tty_ldisc_kill(struct tty_struct *tty) { + lockdep_assert_held_exclusive(&tty->ldisc_sem); if (!tty->ldisc) return; /* @@ -669,6 +672,7 @@ int tty_ldisc_reinit(struct tty_struct *tty, int disc) struct tty_ldisc *ld; int retval; + lockdep_assert_held_exclusive(&tty->ldisc_sem); ld = tty_ldisc_get(tty, disc); if (IS_ERR(ld)) { BUG_ON(disc == N_TTY); @@ -767,6 +771,10 @@ int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) return retval; if (o_tty) { + /* + * Called without o_tty->ldisc_sem held, as o_tty has been + * just allocated and no one has a reference to it. + */ retval = tty_ldisc_open(o_tty, o_tty->ldisc); if (retval) { tty_ldisc_close(tty, tty->ldisc); @@ -832,6 +840,7 @@ 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; |