Hi all,
Three fixes that worth to have in the @stable, as they were hit by different people, including Arista 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 an optional and probably, timeout can be dropped for read_lock(). I'll do it if everyone agrees. (Or as per discussion with Peter in v3, just convert ldisc to a regular rwsem).
Thanks, Dima
Changes since v4: - back to lock ldisc with (5*HZ) timeout in tty_reopen() (LKP report link: lkml.kernel.org/r/1536940609.3185.29.camel@arista.com) - reordered 3/7 with 2/7 for LKP robot
Changes since v3: - Added tested-by Mark Rutland (thanks!) - Dropped patch with smp_wmb() - wrong idea - lockdep_assert_held() should be actually lockdep_assert_held_exclusive() - Described why tty_ldisc_open() can be called without ldisc_sem held for pty slave end (o_tty). - Added Peter's patch for dropping self-made lockdep annotations - Fix for a reader(s) of ldisc semaphore waiting for an active reader(s)
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 v2 link: lkml.kernel.org/r/20180903165257.29227-1-dima@arista.com v3 link: lkml.kernel.org/r/20180911014821.26286-1-dima@arista.com v4 link: lkml.kernel.org/r/20180912001702.18522-1-dima@arista.com
Cc: Daniel Axtens dja@axtens.net Cc: Dmitry Vyukov dvyukov@google.com Cc: Mark Rutland mark.rutland@arm.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: Peter Zijlstra peterz@infradead.org 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: Wake up readers after timed out down_write() tty: Hold tty_ldisc_lock() during tty_reopen() tty: Simplify tty->count math in tty_reopen() tty/ldsem: Add lockdep asserts for ldisc_sem tty/ldsem: Decrement wait_readers on timeouted down_read()
Peter Zijlstra (1): tty/ldsem: Convert to regular lockdep annotations
drivers/tty/tty_io.c | 13 ++++++++--- drivers/tty/tty_ldisc.c | 9 +++++++ drivers/tty/tty_ldsem.c | 62 ++++++++++++++++++++----------------------------- 3 files changed, 44 insertions(+), 40 deletions(-)