linux-kernel - [PATCH 3.12 47/78] xen/events: Mask a moving irq

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: <bc2d8a1f629272916b402b40d54bd3ac4c0c6595.1461323133.git.jslaby@suse.cz>
Date:	Fri, 22 Apr 2016 13:05:30 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	David Vrabel <david.vrabel@...rix.com>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 47/78] xen/events: Mask a moving irq

From: Boris Ostrovsky <boris.ostrovsky@...cle.com>

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

===============

commit ff1e22e7a638a0782f54f81a6c9cb139aca2da35 upstream.

Moving an unmasked irq may result in irq handler being invoked on both
source and target CPUs.

With 2-level this can happen as follows:

On source CPU:
        evtchn_2l_handle_events() ->
            generic_handle_irq() ->
                handle_edge_irq() ->
                   eoi_pirq():
                       irq_move_irq(data);

                       /***** WE ARE HERE *****/

                       if (VALID_EVTCHN(evtchn))
                           clear_evtchn(evtchn);

If at this moment target processor is handling an unrelated event in
evtchn_2l_handle_events()'s loop it may pick up our event since target's
cpu_evtchn_mask claims that this event belongs to it *and* the event is
unmasked and still pending. At the same time, source CPU will continue
executing its own handle_edge_irq().

With FIFO interrupt the scenario is similar: irq_move_irq() may result
in a EVTCHNOP_unmask hypercall which, in turn, may make the event
pending on the target CPU.

We can avoid this situation by moving and clearing the event while
keeping event masked.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Signed-off-by: David Vrabel <david.vrabel@...rix.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 drivers/xen/events.c | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index bd12a6660fe3..3715a54117bb 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -573,9 +573,19 @@ static void eoi_pirq(struct irq_data *data)
 	struct physdev_eoi eoi = { .irq = pirq_from_irq(data->irq) };
 	int rc = 0;
 
-	irq_move_irq(data);
+	if (!VALID_EVTCHN(evtchn))
+		return;
 
-	if (VALID_EVTCHN(evtchn))
+	if (unlikely(irqd_is_setaffinity_pending(data))) {
+		int masked = test_and_set_mask(evtchn);
+
+		clear_evtchn(evtchn);
+
+		irq_move_masked_irq(data);
+
+		if (!masked)
+			unmask_evtchn(evtchn);
+	} else
 		clear_evtchn(evtchn);
 
 	if (pirq_needs_eoi(data->irq)) {
@@ -1603,9 +1613,19 @@ static void ack_dynirq(struct irq_data *data)
 {
 	int evtchn = evtchn_from_irq(data->irq);
 
-	irq_move_irq(data);
+	if (!VALID_EVTCHN(evtchn))
+		return;
 
-	if (VALID_EVTCHN(evtchn))
+	if (unlikely(irqd_is_setaffinity_pending(data))) {
+		int masked = test_and_set_mask(evtchn);
+
+		clear_evtchn(evtchn);
+
+		irq_move_masked_irq(data);
+
+		if (!masked)
+			unmask_evtchn(evtchn);
+	} else
 		clear_evtchn(evtchn);
 }
 
-- 
2.8.1