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 <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
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 <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Reported-by: syzbot <syzbot+40b7287c2dc987c48c81@xxxxxxxxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Vegard Nossum <vegard.nossum@xxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Jiri Slaby <jslaby@xxxxxxxx>
Cc: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
Cc: One Thousand Gnomes <gnomes@xxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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