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cpuidle: Avoid potential overflow in integer multiplication
In detail: In C language, when you perform a multiplication operation, if both operands are of int type, the multiplication operation is performed on the int type, and then the result is converted to the target type. This means that if the product of int type multiplication exceeds the range that int type can represent, an overflow will occur even if you store the result in a variable of int64_t type. For a multiplication of two int values, it is better to use mul_u32_u32() rather than s->exit_latency_ns = s->exit_latency * NSEC_PER_USEC to avoid potential overflow happenning. Signed-off-by: C Cheng <C.Cheng@mediatek.com> Signed-off-by: Bo Ye <bo.ye@mediatek.com> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com> [ rjw: New subject ] Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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@ -16,6 +16,7 @@
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#include <linux/cpumask.h>
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#include <linux/tick.h>
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#include <linux/cpu.h>
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#include <linux/math64.h>
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#include "cpuidle.h"
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@ -187,7 +188,7 @@ static void __cpuidle_driver_init(struct cpuidle_driver *drv)
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s->target_residency = div_u64(s->target_residency_ns, NSEC_PER_USEC);
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if (s->exit_latency > 0)
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s->exit_latency_ns = s->exit_latency * NSEC_PER_USEC;
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s->exit_latency_ns = mul_u32_u32(s->exit_latency, NSEC_PER_USEC);
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else if (s->exit_latency_ns < 0)
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s->exit_latency_ns = 0;
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else
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