tty: Don't call panic() at tty_ldisc_init()

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=883431818e036ae6a9981156a64b821110f39187

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>

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 52627478ab617c302643aabf520b90c59eab1926..562d31073f9a2c588c62de7f0d64c570bf9fcf62 100644 (file)
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2815,7 +2815,10 @@ struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx)
 
        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);

diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index 7c895684c3efd1892913f31a9d093d90d1238f33..77eac4ab173704b4811cd262298d2bc4dbebb29e 100644 (file)
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -823,12 +823,13 @@ EXPORT_SYMBOL_GPL(tty_ldisc_release);
  *     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;
 }
 
 /**

diff --git a/include/linux/tty.h b/include/linux/tty.h
index 47f8af22f2168f0376d77068ecbc2df930ae8f79..1dd587ba6d882bb882b44680ec1acebb314c4364 100644 (file)
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -701,7 +701,7 @@ extern int tty_unregister_ldisc(int disc);
 extern int tty_set_ldisc(struct tty_struct *tty, int disc);
 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 int tty_ldisc_receive_buf(struct tty_ldisc *ld, const unsigned char *p,
                                 char *f, int count);