Hi all,
Three fixes that worth to have in the @stable, as we've hit them on v4.9 stable.
And for linux-next - adding lockdep asserts for line discipline changing code, verifying that write ldisc sem will be held forthwith.
The last patch is optional and probably, timeout can be dropped for read_lock(). I'll do it if everyone agrees.
Rong Chen, could you kindly re-run this version to see if the lockup from v1 still happens? I wasn't able to reproduce it..
Thanks, Dima
Changes since v2: - Added reviewed-by tags - Hopefully, fixed reported by 0-day issue. - Added optional fix for wait_readers decrement
Changes since v1: - Added tested-by/reported-by tags - Dropped 3/4 (locking tty pair for lockdep sake), Because of that - not adding lockdep_assert_held() in tty_ldisc_open() - Added 4/4 cleanup to inc tty->count only on success of tty_ldisc_reinit() - lock ldisc without (5*HZ) timeout in tty_reopen()
v1 link: lkml.kernel.org/r/20180829022353.23568-1-dima@arista.com
Huuge cc list: Cc: Daniel Axtens dja@axtens.net Cc: Dmitry Vyukov dvyukov@google.com Cc: Michael Neuling mikey@neuling.org Cc: Mikulas Patocka mpatocka@redhat.com Cc: Nathan March nathan@gt.net Cc: Pasi Kärkkäinen pasik@iki.fi Cc: Peter Hurley peter@hurleysoftware.com Cc: "Rong, Chen" rong.a.chen@intel.com Cc: Sergey Senozhatsky sergey.senozhatsky.work@gmail.com Cc: Tan Xiaojun tanxiaojun@huawei.com Cc: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp (please, ignore if I Cc'ed you mistakenly)
Dmitry Safonov (6): tty: Drop tty->count on tty_reopen() failure tty/ldsem: Update waiter->task before waking up reader tty: Hold tty_ldisc_lock() during tty_reopen() tty/lockdep: Add ldisc_sem asserts tty: Simplify tty->count math in tty_reopen() tty/ldsem: Decrement wait_readers on timeouted down_read()
drivers/tty/tty_io.c | 12 ++++++++---- drivers/tty/tty_ldisc.c | 5 +++++ drivers/tty/tty_ldsem.c | 5 ++++- 3 files changed, 17 insertions(+), 5 deletions(-)