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Message-ID: <lsq.1539530741.275311387@decadent.org.uk>
Date: Sun, 14 Oct 2018 16:25:41 +0100
From: Ben Hutchings <ben@...adent.org.uk>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC: akpm@...ux-foundation.org, "Dmitry Vyukov" <dvyukov@...gle.com>,
"Jiri Slaby" <jslaby@...e.com>,
"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
"Peter Hurley" <peter@...leysoftware.com>,
"Tetsuo Handa" <penguin-kernel@...ove.SAKURA.ne.jp>,
"Michal Hocko" <mhocko@...e.com>,
"Linus Torvalds" <torvalds@...ux-foundation.org>,
"Vegard Nossum" <vegard.nossum@...il.com>,
"One Thousand Gnomes" <gnomes@...rguk.ukuu.org.uk>,
"syzbot" <syzbot+40b7287c2dc987c48c81@...kaller.appspotmail.com>
Subject: [PATCH 3.16 221/366] tty: Use __GFP_NOFAIL for tty_ldisc_get()
3.16.60-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
commit bcdd0ca8cb8730573afebcaae4138f8f4c8eaa20 upstream.
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@...ove.SAKURA.ne.jp>
Reported-by: syzbot <syzbot+40b7287c2dc987c48c81@...kaller.appspotmail.com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Vegard Nossum <vegard.nossum@...il.com>
Cc: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Jiri Slaby <jslaby@...e.com>
Cc: Peter Hurley <peter@...leysoftware.com>
Cc: One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
drivers/tty/tty_ldisc.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -171,12 +171,11 @@ static struct tty_ldisc *tty_ldisc_get(s
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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