Commit bcdd0ca8 authored Apr 25, 2018 by Tetsuo Handa Committed by Greg Kroah-Hartman Apr 25, 2018

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 5362544b ("tty: don't panic on OOM in
tty_set_ldisc()"). But we reverted that attempt by commit a8983d01
("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 <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: syzbot <syzbot+40b7287c2dc987c48c81@syzkaller.appspotmail.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 66dd99c2

drivers/tty/tty_ldisc.c

+5 −6

Original line number	Diff line number	Diff line
		@@ -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;

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