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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4891cca5743sm95937205e9.9.2026.04.20.11.46.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Apr 2026 11:46:27 -0700 (PDT) Date: Mon, 20 Apr 2026 19:46:24 +0100 From: David Laight To: Agalakov Daniil Cc: Steve Longerbeam , Sakari Ailus , Mauro Carvalho Chehab , Maxime Ripard , Jacopo Mondi , , , , Roman Razov Subject: Re: [PATCH] media: i2c: ov5640: Fix potential integer overflow in sysclk calculation Message-ID: <20260420194624.695dbae0@pumpkin> In-Reply-To: <20260420154007.2877949-1-ade@amicon.ru> References: <20260420154007.2877949-1-ade@amicon.ru> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 20 Apr 2026 18:39:50 +0300 Agalakov Daniil wrote: > The calculation of sysclk uses 32-bit arithmetic because > sensor->xclk_freq is a 32-bit integer. The intermediate multiplication > result can overflow 32 bits sysclk variable. > > For example, with pll_prediv fixed at 3 (OV5640_PLL_PREDIV), xclk_freq > set to its maximum of 54MHz (OV5640_XCLK_MAX) and a pll_mult value above > 238 (the maximum value for pll_mult is 252, defined as > OV5640_PLL_MULT_MAX), the result exceeds the 32-bit limit. > > This overflow causes the 1GHz safety check to fail, as the truncated > value fits within the 1GHz limit. Consequently, the function returns an > incorrect frequency, leading to misconfiguration of the sensor. > > Explicitly cast the first operand to u64 to ensure the entire expression > is evaluated in 64-bit precision. > > Found by Linux Verification Center (linuxtesting.org) with SVACE. > > Fixes: aa2882481cad ("media: ov5640: Adjust the clock based on the expected rate") > Signed-off-by: Agalakov Daniil > --- > drivers/media/i2c/ov5640.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/media/i2c/ov5640.c b/drivers/media/i2c/ov5640.c > index 85ecc23b3587..04e5a683976a 100644 > --- a/drivers/media/i2c/ov5640.c > +++ b/drivers/media/i2c/ov5640.c > @@ -1377,7 +1377,7 @@ static unsigned long ov5640_compute_sys_clk(struct ov5640_dev *sensor, > u8 pll_prediv, u8 pll_mult, > u8 sysdiv) > { > - unsigned long sysclk = sensor->xclk_freq / pll_prediv * pll_mult; > + u64 sysclk = (u64)sensor->xclk_freq / pll_prediv * pll_mult; > > /* PLL1 output cannot exceed 1GHz. */ > if (sysclk / 1000000 > 1000) It would be much better to rework the test to avoid a 64bit divide (which will fail to compile on 32bit). Even the 'sysclk / 1000000 > 1000' test may fail to compile, the compiler might convert it so the equivalent 'sysclk > 1000999999' to avoid the division. I don't know if that is the correct test - it doesn't match the comment. You could do something like: u32 sysclk; if ((sensor->xclk_freq >> 8) * pll_mult > (2000000000 >> 8) * pll_prediv) /* output would be over 2GHz (or thereabouts) */ ... sysclk = sensor->xclk_freq / pll_prediv * pll_mult; if (sysclk > 1000000000) /* output is over 1GHz */ David