This is a note to let you know that I've just added the patch titled
clocksource/drivers/arm_global_timer: Guard against division by zero
to the 6.6-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:
clocksource-drivers-arm_global_timer-guard-against-d.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 4b4edbb1096e44864dc5e0b4c4975462e6f4f906
Author: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
Date: Sun Feb 25 16:13:35 2024 +0100
clocksource/drivers/arm_global_timer: Guard against division by zero
[ Upstream commit e651f2fae33634175fae956d896277cf916f5d09 ]
The result of the division of new_rate by gt_target_rate can be zero (if
new_rate is smaller than gt_target_rate). Using that result as divisor
without checking can result in a division by zero error. Guard against
this by checking for a zero value earlier.
While here, also change the psv variable to an unsigned long to make
sure we don't overflow the datatype as all other types involved are also
unsiged long.
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
Signed-off-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240225151336.2728533-3-martin.blumenstingl@xxxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/clocksource/arm_global_timer.c b/drivers/clocksource/arm_global_timer.c
index e1c773bb55359..22a58d35a41fa 100644
--- a/drivers/clocksource/arm_global_timer.c
+++ b/drivers/clocksource/arm_global_timer.c
@@ -290,18 +290,17 @@ static int gt_clk_rate_change_cb(struct notifier_block *nb,
switch (event) {
case PRE_RATE_CHANGE:
{
- int psv;
+ unsigned long psv;
- psv = DIV_ROUND_CLOSEST(ndata->new_rate,
- gt_target_rate);
-
- if (abs(gt_target_rate - (ndata->new_rate / psv)) > MAX_F_ERR)
+ psv = DIV_ROUND_CLOSEST(ndata->new_rate, gt_target_rate);
+ if (!psv ||
+ abs(gt_target_rate - (ndata->new_rate / psv)) > MAX_F_ERR)
return NOTIFY_BAD;
psv--;
/* prescaler within legal range? */
- if (psv < 0 || psv > GT_CONTROL_PRESCALER_MAX)
+ if (psv > GT_CONTROL_PRESCALER_MAX)
return NOTIFY_BAD;
/*
