[tip: irq/urgent] genirq/timings: Prevent potential array overflow in __irq_timings_store()

The following commit has been merged into the irq/urgent branch of tip:

Commit-ID:     b9cc7d8a4656a6e815852c27ab50365009cb69c1
Gitweb:        https://git.kernel.org/tip/b9cc7d8a4656a6e815852c27ab50365009cb69c1
Author:        Ben Dai [off-list ref]
AuthorDate:    Sun, 25 Apr 2021 23:09:03 +08:00
Committer:     Thomas Gleixner [off-list ref]
CommitterDate: Tue, 10 Aug 2021 15:39:00 +02:00

genirq/timings: Prevent potential array overflow in __irq_timings_store()

When the interrupt interval is greater than 2 ^ PREDICTION_BUFFER_SIZE *
PREDICTION_FACTOR us and less than 1s, the calculated index will be greater
than the length of irqs->ema_time[]. Check the calculated index before
using it to prevent array overflow.

Fixes: 23aa3b9a6b7d ("genirq/timings: Encapsulate storing function")
Signed-off-by: Ben Dai <redacted>
Signed-off-by: Thomas Gleixner <redacted>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210425150903.25456-1-ben.dai9703@gmail.com (local)

---
 kernel/irq/timings.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/irq/timings.c b/kernel/irq/timings.c
index d309d6f..4d2a702 100644
--- a/kernel/irq/timings.c
+++ b/kernel/irq/timings.c

@@ -453,6 +453,11 @@ static __always_inline void __irq_timings_store(int irq, struct irqt_stat *irqs,
 	 */
 	index = irq_timings_interval_index(interval);
 
+	if (index > PREDICTION_BUFFER_SIZE - 1) {
+		irqs->count = 0;
+		return;
+	}
+
 	/*
 	 * Store the index as an element of the pattern in another
 	 * circular array.