4.4-stable review patch. If anyone has any objections, please let me know.
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From: Tetsuo Handa penguin-kernel@I-love.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=489d33fa386453859ead58ff5171d43772b13aa...
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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 @@ -168,12 +168,11 @@ 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;