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[PATCH v2 3/3] arinc653: avoid array overrun
- To: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 25 Mar 2026 13:55:15 +0100
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- Cc: Nathan Studer <nathan.studer@xxxxxxxxxxxxxxx>, Stewart Hildebrand <stewart@xxxxxxx>, Kamil Frankowicz <kamil.frankowicz@xxxxxxx>, Juergen Gross <jgross@xxxxxxxx>
- Delivery-date: Wed, 25 Mar 2026 12:55:20 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
Incrementing ->sched_index between bounds check and array access may
result in accessing one past the array when that is fully filled
(->num_schedule_entries == ARINC653_MAX_DOMAINS_PER_SCHEDULE).
Fixes: 22787f2e107c ("ARINC 653 scheduler")
Reported-by: Kamil Frankowicz <kamil.frankowicz@xxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
Jürgen, provided I understood him correctly, suggests that something like
while ( now >= sched_priv->next_switch_time )
{
sched_priv->sched_index++;
ASSERT(sched_priv->sched_index < sched_priv->num_schedule_entries);
sched_priv->next_switch_time +=
sched_priv->schedule[sched_priv->sched_index].runtime;
}
should also be valid to move to, due to constraints applied by
arinc653_sched_set(). I'm hesitant to make such a change though, not
really knowing the scheduler; the change here looks more obviously correct
to me. Albeit the Fixes: tag may thus want dropping.
---
v2: New.
--- a/xen/common/sched/arinc653.c
+++ b/xen/common/sched/arinc653.c
@@ -552,12 +552,9 @@ a653sched_do_schedule(
/* Switch minor frame or find correct minor frame after a miss */
while ( (now >= sched_priv->next_switch_time) &&
- (sched_priv->sched_index < sched_priv->num_schedule_entries) )
- {
- sched_priv->sched_index++;
+ (++sched_priv->sched_index < sched_priv->num_schedule_entries) )
sched_priv->next_switch_time +=
sched_priv->schedule[sched_priv->sched_index].runtime;
- }
/*
* If we exhausted the domains in the schedule and still have time left
|
