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Thu, 20 Nov 2025 07:53:57 -0800 (PST) Received: from [192.168.1.96] ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id 8926c6da1cb9f-5b954b207ccsm1076224173.34.2025.11.20.07.53.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 20 Nov 2025 07:53:57 -0800 (PST) Message-ID: <312fe285-3915-4108-bc49-3357977d644d@kernel.dk> Date: Thu, 20 Nov 2025 08:53:56 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 04/44] io_uring/net: Change some dubious min_t() To: David Laight Cc: linux-kernel@vger.kernel.org, io-uring@vger.kernel.org References: <20251119224140.8616-1-david.laight.linux@gmail.com> <20251119224140.8616-5-david.laight.linux@gmail.com> <3202c47d-532d-4c74-aff9-992ec1d9cbeb@kernel.dk> <20251120154817.0160eeac@pumpkin> Content-Language: en-US From: Jens Axboe In-Reply-To: <20251120154817.0160eeac@pumpkin> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/20/25 8:48 AM, David Laight wrote: > On Thu, 20 Nov 2025 07:48:58 -0700 > Jens Axboe wrote: > >> On 11/19/25 3:41 PM, david.laight.linux@gmail.com wrote: >>> From: David Laight >>> >>> Since iov_len is 'unsigned long' it is possible that the cast >>> to 'int' will change the value of min_t(int, iov[nbufs].iov_len, ret). >>> Use a plain min() and change the loop bottom to while (ret > 0) so that >>> the compiler knows 'ret' is always positive. >>> >>> Also change min_t(int, sel->val, sr->mshot_total_len) to a simple min() >>> since sel->val is also long and subject to possible trunctation. >>> >>> It might be that other checks stop these being problems, but they are >>> picked up by some compile-time tests for min_t() truncating values. >> >> Fails with clang-21: >> >> io_uring/net.c:855:26: error: call to '__compiletime_assert_2006' declared with 'error' attribute: min(sel->val, sr->mshot_total_len) signedness error >> 855 | sr->mshot_total_len -= min(sel->val, sr->mshot_total_len); > > I'll take a look, I normally use gcc but there must be something > subtle going on. Actually which architecture? I only tested x86-64. This is x86-64. -- Jens Axboe