Messages in this thread Patch in this message | | | From | Bo Ye <> | Subject | [PATCH] cpuidle: idle exit_latency overflow | Date | Thu, 16 Nov 2023 21:26:19 +0800 |
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From: mtk24676 <C.Cheng@mediatek.com>
In detail: In kernel-6.1, in the __cpuidle_driver_init function in driver/cpuidle/driver.c, there is a line of code that causes an overflow. The line is s->exit_latency_ns = s->exit_latency * NSEC_PER_USEC. The overflow occurs because the product of an int type and a constant exceeds the range of the int type.
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.
Signed-off-by: mtk24676 <C.Cheng@mediatek.com> Signed-off-by: bo.ye <bo.ye@mediatek.com> ---
diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c index d9cda7f..631ca16 100644 --- a/drivers/cpuidle/driver.c +++ b/drivers/cpuidle/driver.c @@ -187,7 +187,7 @@ s->target_residency = div_u64(s->target_residency_ns, NSEC_PER_USEC); if (s->exit_latency > 0) - s->exit_latency_ns = s->exit_latency * NSEC_PER_USEC; + s->exit_latency_ns = (u64)s->exit_latency * NSEC_PER_USEC; else if (s->exit_latency_ns < 0) s->exit_latency_ns = 0; else
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