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Re: [PATCH v2 3/3] arinc653: avoid array overrun
- To: Jan Beulich <jbeulich@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Jürgen Groß <jgross@xxxxxxxx>
- Date: Wed, 25 Mar 2026 14:22:35 +0100
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- Cc: Nathan Studer <nathan.studer@xxxxxxxxxxxxxxx>, Stewart Hildebrand <stewart@xxxxxxx>, Kamil Frankowicz <kamil.frankowicz@xxxxxxx>
- Delivery-date: Wed, 25 Mar 2026 13:22:44 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 25.03.26 13:55, Jan Beulich wrote:
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>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
with ...
---
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.
the Fixes: tag dropped, as the constraints mentioned are IMO really enough
to avoid an issue.
I agree that the current code is far from obviously correct, so your patch
is definitively an improvement.
Juergen
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