4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp
commit 903f9db10f18f735e62ba447147b6c434b6af003 upstream.
syzbot is reporting kernel panic [1] triggered by memory allocation failure at tty_ldisc_get() from tty_ldisc_init(). But since both tty_ldisc_get() and caller of tty_ldisc_init() can cleanly handle errors, tty_ldisc_init() does not need to call panic() when tty_ldisc_get() failed.
[1] https://syzkaller.appspot.com/bug?id=883431818e036ae6a9981156a64b821110f3918...
Signed-off-by: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp Reported-by: syzbot syzkaller@googlegroups.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Jiri Slaby jslaby@suse.com Cc: stable stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/tty/tty_io.c | 5 ++++- drivers/tty/tty_ldisc.c | 5 +++-- include/linux/tty.h | 2 +- 3 files changed, 8 insertions(+), 4 deletions(-)
--- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -3154,7 +3154,10 @@ struct tty_struct *alloc_tty_struct(stru
kref_init(&tty->kref); tty->magic = TTY_MAGIC; - tty_ldisc_init(tty); + if (tty_ldisc_init(tty)) { + kfree(tty); + return NULL; + } tty->session = NULL; tty->pgrp = NULL; mutex_init(&tty->legacy_mutex); --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -804,12 +804,13 @@ void tty_ldisc_release(struct tty_struct * the tty structure is not completely set up when this call is made. */
-void tty_ldisc_init(struct tty_struct *tty) +int tty_ldisc_init(struct tty_struct *tty) { struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY); if (IS_ERR(ld)) - panic("n_tty: init_tty"); + return PTR_ERR(ld); tty->ldisc = ld; + return 0; }
/** --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -586,7 +586,7 @@ extern int tty_unregister_ldisc(int disc extern int tty_set_ldisc(struct tty_struct *tty, int ldisc); extern int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty); extern void tty_ldisc_release(struct tty_struct *tty); -extern void tty_ldisc_init(struct tty_struct *tty); +extern int __must_check tty_ldisc_init(struct tty_struct *tty); extern void tty_ldisc_deinit(struct tty_struct *tty); extern void tty_ldisc_begin(void);