From mboxrd@z Thu Jan 1 00:00:00 1970 From: walter harms Date: Tue, 22 Oct 2019 12:46:21 +0000 Subject: Re: [PATCH][next] drivers: thermal: tsens: fix potential integer overflow on multiply Message-Id: <5DAEFA1D.8070508@bfs.de> List-Id: References: <20191022114910.652-1-colin.king@canonical.com> In-Reply-To: <20191022114910.652-1-colin.king@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Colin King Cc: Amit Kucheria , Andy Gross , Zhang Rui , Eduardo Valentin , Daniel Lezcano , Stephen Boyd , linux-pm@vger.kernel.org, linux-arm-msm@vger.kernel.org, kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org Am 22.10.2019 13:49, schrieb Colin King: > From: Colin Ian King > > Currently a multiply operation is being performed on two int values > and the result is being assigned to a u64, presumably because the > end result is expected to be probably larger than an int. However, > because the multiply is an int multiply one can get overflow. Avoid > the overflow by casting degc to a u64 to force a u64 multiply. > > Addresses-Coverity: ("Unintentional integer overflow") > Fixes: fbfe1a042cfd ("drivers: thermal: tsens: Add interrupt support") > Signed-off-by: Colin Ian King > --- > drivers/thermal/qcom/tsens-common.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/thermal/qcom/tsens-common.c b/drivers/thermal/qcom/tsens-common.c > index 03bf1b8133ea..3d7855106ecd 100644 > --- a/drivers/thermal/qcom/tsens-common.c > +++ b/drivers/thermal/qcom/tsens-common.c > @@ -92,7 +92,7 @@ void compute_intercept_slope(struct tsens_priv *priv, u32 *p1, > > static inline u32 degc_to_code(int degc, const struct tsens_sensor *s) > { > - u64 code = (degc * s->slope + s->offset) / SLOPE_FACTOR; > + u64 code = ((u64)degc * s->slope + s->offset) / SLOPE_FACTOR; > looks ok just to offer an alternative to avoid the cast; u64 code = degc; code = code * s->slope + s->offset; code/=SLOPE_FACTOR; ym2c re, wh > pr_debug("%s: raw_code: 0x%llx, degc:%d\n", __func__, code, degc); > return clamp_val(code, THRESHOLD_MIN_ADC_CODE, THRESHOLD_MAX_ADC_CODE);