linux-kernel - [PATCH 3.13 129/162] usb: musb: cppi41: restart hrtimer only if not yet done

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

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1415313426-9622-130-git-send-email-kamal@canonical.com>
Date:	Thu,  6 Nov 2014 14:36:33 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Felipe Balbi <balbi@...com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.13 129/162] usb: musb: cppi41: restart hrtimer only if not yet done

3.13.11.11 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <tglx@...utronix.de>

commit d2e6d62c9cbbc2da4211f672dbeea08960e29a80 upstream.

commit c58d80f52 ("usb: musb: Ensure that cppi41 timer gets armed on
premature DMA TX irq") fixed hrtimer scheduling bug. There is one left
which does not trigger that often.
The following scenario is still possible:

    lock(&x->lock);
    hrtimer_start(&x->t);
    unlock(&x->lock);

expires:
    t->function();
                                lock(&x->lock);
    lock(&x->lock);             if (!hrtimer_queued(&x->t))
                                        hrtimer_start(&x->t);
                                unlock(&x->lock);

    if (!list_empty(x->early_tx_list))
           ret = HRTIMER_RESTART;
->         hrtimer_forward_now(...)
    } else
           ret = HRTIMER_NORESTART;

    unlock(&x->lock);

and the timer callback returns HRTIMER_RESTART for an armed timer. This
is wrong and we run into the BUG_ON() in __run_hrtimer().
This can happens on SMP or PREEMPT-RT.
The patch fixes the problem by only starting the timer if the timer is
not yet queued.

Reported-by: Torben Hohn <torbenh@...utronix.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
[bigeasy: collected information and created a patch + description based
          on it]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Signed-off-by: Felipe Balbi <balbi@...com>

Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/usb/musb/musb_cppi41.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/musb/musb_cppi41.c b/drivers/usb/musb/musb_cppi41.c
index 4a5af5c..3faaeb7 100644
--- a/drivers/usb/musb/musb_cppi41.c
+++ b/drivers/usb/musb/musb_cppi41.c
@@ -190,7 +190,8 @@ static enum hrtimer_restart cppi41_recheck_tx_req(struct hrtimer *timer)
 		}
 	}
 
-	if (!list_empty(&controller->early_tx_list)) {
+	if (!list_empty(&controller->early_tx_list) &&
+	    !hrtimer_is_queued(&controller->early_tx)) {
 		ret = HRTIMER_RESTART;
 		hrtimer_forward_now(&controller->early_tx,
 				ktime_set(0, 150 * NSEC_PER_USEC));
-- 
1.9.1

--
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/