| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Wed, 31 Jul 2013 15:47:26 +0400
From: Artem Savkov <artem.savkov@...il.com>
To: Peter Hurley <peter@...leysoftware.com>
Cc: Michel Lespinasse <walken@...gle.com>, gregkh@...uxfoundation.org,
jslaby@...e.cz, linux-kernel@...r.kernel.org,
Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] n_tty: release atomic_read_lock before calling
schedule_timeout()
On Tue, Jul 30, 2013 at 12:39:54PM -0400, Peter Hurley wrote:
> On 07/30/2013 11:35 AM, Artem Savkov wrote:
> >ldata->atomic_read_lock should be released before scheduling as well as
> >tty->termios_rwsem, otherwise there is a potential deadlock detected by lockdep
>
> False positive.
>
> >Introduced in "n_tty: Access termios values safely"
> >(9356b535fcb71db494fc434acceb79f56d15bda2 in linux-next.git)
> >
> >[ 16.822058] ======================================================
> >[ 16.822058] [ INFO: possible circular locking dependency detected ]
> >[ 16.822058] 3.11.0-rc3-next-20130730+ #140 Tainted: G W
> >[ 16.822058] -------------------------------------------------------
> >[ 16.822058] bash/1198 is trying to acquire lock:
> >[ 16.822058] (&tty->termios_rwsem){++++..}, at: [<ffffffff816aa3bb>] n_tty_read+0x49b/0x660
> >[ 16.822058]
> >[ 16.822058] but task is already holding lock:
> >[ 16.822058] (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff816aa0f0>] n_tty_read+0x1d0/0x660
> >[ 16.822058]
> >[ 16.822058] which lock already depends on the new lock.
> >[ 16.822058]
> >[ 16.822058]
> >[ 16.822058] the existing dependency chain (in reverse order) is:
> >[ 16.822058]
> >-> #1 (&ldata->atomic_read_lock){+.+...}:
> >[ 16.822058] [<ffffffff811111cc>] validate_chain+0x73c/0x850
> >[ 16.822058] [<ffffffff811117e0>] __lock_acquire+0x500/0x5d0
> >[ 16.822058] [<ffffffff81111a29>] lock_acquire+0x179/0x1d0
> >[ 16.822058] [<ffffffff81d34b9c>] mutex_lock_interruptible_nested+0x7c/0x540
> >[ 16.822058] [<ffffffff816aa0f0>] n_tty_read+0x1d0/0x660
> >[ 16.822058] [<ffffffff816a3bb6>] tty_read+0x86/0xf0
> >[ 16.822058] [<ffffffff811f21d3>] vfs_read+0xc3/0x130
> >[ 16.822058] [<ffffffff811f2702>] SyS_read+0x62/0xa0
> >[ 16.822058] [<ffffffff81d45259>] system_call_fastpath+0x16/0x1b
> >[ 16.822058]
> >-> #0 (&tty->termios_rwsem){++++..}:
> >[ 16.822058] [<ffffffff8111064f>] check_prev_add+0x14f/0x590
> >[ 16.822058] [<ffffffff811111cc>] validate_chain+0x73c/0x850
> >[ 16.822058] [<ffffffff811117e0>] __lock_acquire+0x500/0x5d0
> >[ 16.822058] [<ffffffff81111a29>] lock_acquire+0x179/0x1d0
> >[ 16.822058] [<ffffffff81d372c1>] down_read+0x51/0xa0
> >[ 16.822058] [<ffffffff816aa3bb>] n_tty_read+0x49b/0x660
> >[ 16.822058] [<ffffffff816a3bb6>] tty_read+0x86/0xf0
> >[ 16.822058] [<ffffffff811f21d3>] vfs_read+0xc3/0x130
> >[ 16.822058] [<ffffffff811f2702>] SyS_read+0x62/0xa0
> >[ 16.822058] [<ffffffff81d45259>] system_call_fastpath+0x16/0x1b
> >[ 16.822058]
> >[ 16.822058] other info that might help us debug this:
> >[ 16.822058]
> >[ 16.822058] Possible unsafe locking scenario:
> >[ 16.822058]
> >[ 16.822058] CPU0 CPU1
> >[ 16.822058] ---- ----
> >[ 16.822058] lock(&ldata->atomic_read_lock);
> >[ 16.822058] lock(&tty->termios_rwsem);
> >[ 16.822058] lock(&ldata->atomic_read_lock);
> >[ 16.822058] lock(&tty->termios_rwsem);
> >[ 16.822058]
> >[ 16.822058] *** DEADLOCK ***
>
> This situation is not possible since termios_rwsem is a read/write semaphore;
> CPU1 cannot prevent CPU0 from obtaining a read lock on termios_rwsem.
Oops, yes, sorry.
> This looks like a regression caused by:
>
> commit a51805efae5dda0da66f79268ffcf0715f9dbea4
> Author: Michel Lespinasse <walken@...gle.com>
> Date: Mon Jul 8 14:23:49 2013 -0700
>
> lockdep: Introduce lock_acquire_exclusive()/shared() helper macros
Doesn't seem to be this commit. I see nothing wrong here and just to be
sure I've checked the kernel with this commit reverted. The issue is
still there.
> In lockdep.h, the spinlock/mutex/rwsem/rwlock/lock_map acquire macros have
> different definitions based on the value of CONFIG_PROVE_LOCKING. We have
> separate ifdefs for each of these definitions, which seems redundant.
>
> Introduce lock_acquire_{exclusive,shared,shared_recursive} helpers which
> will have different definitions based on CONFIG_PROVE_LOCKING. Then all
> other helper macros can be defined based on the above ones, which reduces
> the amount of ifdefined code.
>
> Signed-off-by: Michel Lespinasse <walken@...gle.com>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> Signed-off-by: Peter Zijlstra <peterz@...radead.org>
> Cc: Oleg Nesterov <oleg@...hat.com>
> Cc: Lai Jiangshan <laijs@...fujitsu.com>
> Cc: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
> Cc: Rusty Russell <rusty@...tcorp.com.au>
> Cc: Andi Kleen <ak@...ux.intel.com>
> Cc: "Paul E. McKenney" <paulmck@...ibm.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Link: http://lkml.kernel.org/r/20130708212350.6DD1931C15E@corp2gmr1-1.hot.corp.google.com
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
>
>
> >[ 16.822058]
> >[ 16.822058] 2 locks held by bash/1198:
> >[ 16.822058] #0: (&tty->ldisc_sem){.+.+.+}, at: [<ffffffff816ade04>] tty_ldisc_ref_wait+0x24/0x60
> >[ 16.822058] #1: (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff816aa0f0>] n_tty_read+0x1d0/0x660
> >[ 16.822058]
> >[ 16.822058] stack backtrace:
> >[ 16.822058] CPU: 1 PID: 1198 Comm: bash Tainted: G W 3.11.0-rc3-next-20130730+ #140
> >[ 16.822058] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007
> >[ 16.822058] 0000000000000000 ffff880019acdb28 ffffffff81d34074 0000000000000002
> >[ 16.822058] 0000000000000000 ffff880019acdb78 ffffffff8110ed75 ffff880019acdb98
> >[ 16.822058] ffff880019fd0000 ffff880019acdb78 ffff880019fd0638 ffff880019fd0670
> >[ 16.822058] Call Trace:
> >[ 16.822058] [<ffffffff81d34074>] dump_stack+0x59/0x7d
> >[ 16.822058] [<ffffffff8110ed75>] print_circular_bug+0x105/0x120
> >[ 16.822058] [<ffffffff8111064f>] check_prev_add+0x14f/0x590
> >[ 16.822058] [<ffffffff81d3ab5f>] ? _raw_spin_unlock_irq+0x4f/0x70
> >[ 16.822058] [<ffffffff811111cc>] validate_chain+0x73c/0x850
> >[ 16.822058] [<ffffffff8110ae0f>] ? trace_hardirqs_off_caller+0x1f/0x190
> >[ 16.822058] [<ffffffff811117e0>] __lock_acquire+0x500/0x5d0
> >[ 16.822058] [<ffffffff81111a29>] lock_acquire+0x179/0x1d0
> >[ 16.822058] [<ffffffff816aa3bb>] ? n_tty_read+0x49b/0x660
> >[ 16.822058] [<ffffffff81d372c1>] down_read+0x51/0xa0
> >[ 16.822058] [<ffffffff816aa3bb>] ? n_tty_read+0x49b/0x660
> >[ 16.822058] [<ffffffff816aa3bb>] n_tty_read+0x49b/0x660
> >[ 16.822058] [<ffffffff810e4130>] ? try_to_wake_up+0x210/0x210
> >[ 16.822058] [<ffffffff816a3bb6>] tty_read+0x86/0xf0
> >[ 16.822058] [<ffffffff811f21d3>] vfs_read+0xc3/0x130
> >[ 16.822058] [<ffffffff811f2702>] SyS_read+0x62/0xa0
> >[ 16.822058] [<ffffffff815e24ee>] ? trace_hardirqs_on_thunk+0x3a/0x3f
> >[ 16.822058] [<ffffffff81d45259>] system_call_fastpath+0x16/0x1b
> >
> >Signed-off-by: Artem Savkov <artem.savkov@...il.com>
> >---
> > drivers/tty/n_tty.c | 12 ++++++++++++
> > 1 files changed, 12 insertions(+), 0 deletions(-)
> >
> >diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
> >index dd8ae0c..38c09db 100644
> >--- a/drivers/tty/n_tty.c
> >+++ b/drivers/tty/n_tty.c
> >@@ -2203,11 +2203,23 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
> > break;
> > }
> > n_tty_set_room(tty);
> >+ mutex_unlock(&ldata->atomic_read_lock);
> > up_read(&tty->termios_rwsem);
> >
> > timeout = schedule_timeout(timeout);
> >
> > down_read(&tty->termios_rwsem);
> >+ if (file->f_flags & O_NONBLOCK) {
> >+ if (!mutex_trylock(&ldata->atomic_read_lock)) {
> >+ retval = -EAGAIN;
> >+ break;
> >+ }
> >+ } else {
> >+ if (mutex_lock_interruptible(&ldata->atomic_read_lock)) {
> >+ retval = -ERESTARTSYS;
> >+ break;
> >+ }
> >+ }
> > continue;
> > }
> > __set_current_state(TASK_RUNNING);
> >
>
--
Regards,
Artem
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists