6.6-stable review patch. If anyone has any objections, please let me know.
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From: C Cheng C.Cheng@mediatek.com
[ Upstream commit 88390dd788db485912ee7f9a8d3d56fc5265d52f ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/cpuidle/driver.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c index d9cda7f6ccb98..cf5873cc45dc8 100644 --- a/drivers/cpuidle/driver.c +++ b/drivers/cpuidle/driver.c @@ -16,6 +16,7 @@ #include <linux/cpumask.h> #include <linux/tick.h> #include <linux/cpu.h> +#include <linux/math64.h>
#include "cpuidle.h"
@@ -187,7 +188,7 @@ static void __cpuidle_driver_init(struct cpuidle_driver *drv) 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 = mul_u32_u32(s->exit_latency, NSEC_PER_USEC); else if (s->exit_latency_ns < 0) s->exit_latency_ns = 0; else