This is a note to let you know that I've just added the patch titled
xen/events: add a proper barrier to 2-level uevent unmasking
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xen-events-add-a-proper-barrier-to-2-level-uevent-unmasking.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Tue Nov 17 12:38:50 PM CET 2020
From: Juergen Gross <jgross@xxxxxxxx>
Date: Tue, 3 Nov 2020 15:29:00 +0100
Subject: xen/events: add a proper barrier to 2-level uevent unmasking
To: stable@xxxxxxxxxxxxxxx
Message-ID: <20201103142911.21980-4-jgross@xxxxxxxx>
From: Juergen Gross <jgross@xxxxxxxx>
commit 4d3fe31bd993ef504350989786858aefdb877daa upstream.
A follow-up patch will require certain write to happen before an event
channel is unmasked.
While the memory barrier is not strictly necessary for all the callers,
the main one will need it. In order to avoid an extra memory barrier
when using fifo event channels, mandate evtchn_unmask() to provide
write ordering.
The 2-level event handling unmask operation is missing an appropriate
barrier, so add it. Fifo event channels are fine in this regard due to
using sync_cmpxchg().
This is part of XSA-332.
Cc: stable@xxxxxxxxxxxxxxx
Suggested-by: Julien Grall <julien@xxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
Reviewed-by: Wei Liu <wl@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/xen/events/events_2l.c | 2 ++
1 file changed, 2 insertions(+)
--- a/drivers/xen/events/events_2l.c
+++ b/drivers/xen/events/events_2l.c
@@ -91,6 +91,8 @@ static void evtchn_2l_unmask(unsigned po
BUG_ON(!irqs_disabled());
+ smp_wmb(); /* All writes before unmask must be visible. */
+
if (unlikely((cpu != cpu_from_evtchn(port))))
do_hypercall = 1;
else {
Patches currently in stable-queue which might be from jgross@xxxxxxxx are
queue-4.14/xen-blkback-use-lateeoi-irq-binding.patch
queue-4.14/xen-events-block-rogue-events-for-some-time.patch
queue-4.14/xen-pvcallsback-use-lateeoi-irq-binding.patch
queue-4.14/xen-events-fix-race-in-evtchn_fifo_unmask.patch
queue-4.14/xen-events-switch-user-event-channels-to-lateeoi-model.patch
queue-4.14/xen-events-defer-eoi-in-case-of-excessive-number-of-events.patch
queue-4.14/xen-events-add-a-new-late-eoi-evtchn-framework.patch
queue-4.14/xen-events-use-a-common-cpu-hotplug-hook-for-event-channels.patch
queue-4.14/xen-events-avoid-removing-an-event-channel-while-handling-it.patch
queue-4.14/xen-netback-use-lateeoi-irq-binding.patch
queue-4.14/xen-pciback-use-lateeoi-irq-binding.patch
queue-4.14/xen-events-add-a-proper-barrier-to-2-level-uevent-unmasking.patch
queue-4.14/xen-scsiback-use-lateeoi-irq-binding.patch
