Messages in this thread Patch in this message | | | Subject | Re: kernel BUG at drivers/tty/tty_ldisc.c:LINE! | From | Tetsuo Handa <> | Date | Wed, 25 Apr 2018 20:12:31 +0900 |
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From 3606b60f60f5a2053290e7160a6fd3ee40f38a51 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Date: Wed, 25 Apr 2018 15:26:10 +0900 Subject: [PATCH] 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 <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: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 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> --- 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 050f4d6..971a37e 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; -- 1.8.3.1
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