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Wysocki" , Daniel Lezcano , Matthias Brugger , AngeloGioacchino Del Regno CC: , mtk24676 , "bo . ye" , , , , Subject: [PATCH] cpuidle: idle exit_latency overflow Date: Thu, 16 Nov 2023 21:26:19 +0800 Message-ID: <20231116132619.69500-1-bo.ye@mediatek.com> X-Mailer: git-send-email 2.17.0 MIME-Version: 1.0 X-TM-AS-Product-Ver: SMEX-14.0.0.3152-9.1.1006-23728.005 X-TM-AS-Result: No-10--2.336600-8.000000 X-TMASE-MatchedRID: q6Mcoqip180V3w3L8QuNEG3NvezwBrVmgRykyfrH1xlaW2Ktn+I8/hjt AEYMnZ1a+a6+c8HVVTTkY5jnILkv8QfOsX0b+fZzA9lly13c/gF9LQinZ4QefPcjNeVeWlqY+gt Hj7OwNO2mZ396Gt5HhbRDDFNIh3eVt7VBaHOUXTmiHbKhgq+wjecLkJ18YygSpmkWtXcgBB8O5f DUOrhTJDcG0AuzN2tmcPptgJdP32/rxtqtWRjZinZrUbEZipAEiWT09mQz7szw9kH8zAy44aOuV Lnx3A74 X-TM-AS-User-Approved-Sender: No X-TM-AS-User-Blocked-Sender: No X-TMASE-Result: 10--2.336600-8.000000 X-TMASE-Version: SMEX-14.0.0.3152-9.1.1006-23728.005 X-TM-SNTS-SMTP: 4E0647C9374209A165167659E1BEC95B48EA7C03306E9BBFA04062C7CE3E4B892000:8 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231116_052636_989776_4A9A270A X-CRM114-Status: GOOD ( 10.38 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: mtk24676 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 Signed-off-by: bo.ye 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