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([2a00:1098:3142:14:11ee:1594:bd11:4057]) by smtp.gmail.com with ESMTPSA id a3sm4064800wrn.16.2021.09.27.06.21.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Sep 2021 06:21:41 -0700 (PDT) Subject: Re: [PATCH] staging: vc04_services: shut up out-of-range warning To: Dan Carpenter , Arnd Bergmann Cc: Nicolas Saenz Julienne , Greg Kroah-Hartman , Arnd Bergmann , Stefan Wahren , Ojaswin Mujoo , Amarjargal Gundjalam , bcm-kernel-feedback-list@broadcom.com, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org References: <20210927113702.3866843-1-arnd@kernel.org> <20210927122658.GF2048@kadam> From: Phil Elwell Message-ID: <011c53e6-d628-02b7-fc18-ca3165a45f98@raspberrypi.com> Date: Mon, 27 Sep 2021 14:21:41 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <20210927122658.GF2048@kadam> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Dan, On 27/09/2021 13:26, Dan Carpenter wrote: > On Mon, Sep 27, 2021 at 01:36:56PM +0200, Arnd Bergmann wrote: >> From: Arnd Bergmann >> >> The comparison against SIZE_MAX produces a harmless warning on 64-bit >> architectures: >> >> drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c:185:16: error: result of comparison of constant 419244183493398898 with expression of type 'unsigned int' is always false [-Werror,-Wtautological-constant-out-of-range-compare] >> if (num_pages > (SIZE_MAX - sizeof(struct pagelist) - >> ~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> >> Shut up that warning by adding a cast to a longer type. >> >> Fixes: ca641bae6da9 ("staging: vc04_services: prevent integer overflow in create_pagelist()") >> Signed-off-by: Arnd Bergmann >> --- >> drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c >> index b25369a13452..967f10b9582a 100644 >> --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c >> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c >> @@ -182,7 +182,7 @@ create_pagelist(char *buf, char __user *ubuf, >> offset = (uintptr_t)ubuf & (PAGE_SIZE - 1); >> num_pages = DIV_ROUND_UP(count + offset, PAGE_SIZE); >> >> - if (num_pages > (SIZE_MAX - sizeof(struct pagelist) - >> + if ((size_t)num_pages > (SIZE_MAX - sizeof(struct pagelist) - >> sizeof(struct vchiq_pagelist_info)) / >> (sizeof(u32) + sizeof(pages[0]) + >> sizeof(struct scatterlist))) > > The temptation would be to declare "num_pages" as size_t instead of > adding this cost. But then something will complain about the > "pagelistinfo->num_pages = num_pages;" assignment because > "pagelistinfo->num_pages" is a u32. > > The next temptation is to change the SIZE_MAX to UINT_MAX. I didn't > do that originally because I can't test this and I was trying not to > break things... We probably still don't want to break things, but maybe > there is someone who is more familiar with this who knows if UINT_MAX is > okay? The VPU can't address more than 1GB directly, so UINT_MAX is more than sufficient. Phil