From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:36700 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753033AbeDYNEg (ORCPT ); Wed, 25 Apr 2018 09:04:36 -0400 Subject: patch "tty: Use __GFP_NOFAIL for tty_ldisc_get()" added to tty-linus To: penguin-kernel@I-love.SAKURA.ne.jp, dvyukov@google.com, gnomes@lxorguk.ukuu.org.uk, gregkh@linuxfoundation.org, jslaby@suse.com, mhocko@suse.com, peter@hurleysoftware.com, stable@vger.kernel.org, syzbot+40b7287c2dc987c48c81@syzkaller.appspotmail.com, torvalds@linux-foundation.org, vegard.nossum@gmail.com From: Date: Wed, 25 Apr 2018 15:04:28 +0200 Message-ID: <152466146848147@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled tty: Use __GFP_NOFAIL for tty_ldisc_get() to my tty git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git in the tty-linus branch. The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.) The patch will hopefully also be merged in Linus's tree for the next -rc kernel release. If you have any questions about this process, please let me know. >>From bcdd0ca8cb8730573afebcaae4138f8f4c8eaa20 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Wed, 25 Apr 2018 20:12:31 +0900 Subject: tty: Use __GFP_NOFAIL for tty_ldisc_get() syzbot is reporting crashes triggered by memory allocation fault injection at tty_ldisc_get() [1]. As an attempt to handle OOM in a graceful way, we have tried commit 5362544bebe85071 ("tty: don't panic on OOM in tty_set_ldisc()"). But we reverted that attempt by commit a8983d01f9b7d600 ("Revert "tty: don't panic on OOM in tty_set_ldisc()"") due to reproducible crash. We should spend resource for finding and fixing race condition bugs rather than complicate error paths for 2 * sizeof(void *) bytes allocation failure. [1] https://syzkaller.appspot.com/bug?id=489d33fa386453859ead58ff5171d43772b13aa3 Signed-off-by: Tetsuo Handa Reported-by: syzbot Cc: Michal Hocko Cc: Vegard Nossum Cc: Dmitry Vyukov Cc: Jiri Slaby Cc: Peter Hurley Cc: One Thousand Gnomes Cc: Linus Torvalds Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_ldisc.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index 8a88a7787cfe..fb7329ab2b37 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -176,12 +176,11 @@ static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc) return ERR_CAST(ldops); } - ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL); - if (ld == NULL) { - put_ldops(ldops); - return ERR_PTR(-ENOMEM); - } - + /* + * There is no way to handle allocation failure of only 16 bytes. + * Let's simplify error handling and save more memory. + */ + ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL | __GFP_NOFAIL); ld->ops = ldops; ld->tty = tty; -- 2.17.0