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Thu, 20 Nov 2025 06:48:58 -0800 (PST) Message-ID: <3202c47d-532d-4c74-aff9-992ec1d9cbeb@kernel.dk> Date: Thu, 20 Nov 2025 07:48:58 -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.linux@gmail.com, 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> Content-Language: en-US From: Jens Axboe In-Reply-To: <20251119224140.8616-5-david.laight.linux@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit 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); | ^ ./include/linux/minmax.h:105:19: note: expanded from macro 'min' 105 | #define min(x, y) __careful_cmp(min, x, y) | ^ ./include/linux/minmax.h:98:2: note: expanded from macro '__careful_cmp' 98 | __careful_cmp_once(op, x, y, __UNIQUE_ID(x_), __UNIQUE_ID(y_)) | ^ ./include/linux/minmax.h:93:2: note: expanded from macro '__careful_cmp_once' 93 | BUILD_BUG_ON_MSG(!__types_ok(ux, uy), \ | ^ note: (skipping 2 expansions in backtrace; use -fmacro-backtrace-limit=0 to see all) ././include/linux/compiler_types.h:590:2: note: expanded from macro '_compiletime_assert' 590 | __compiletime_assert(condition, msg, prefix, suffix) | ^ ././include/linux/compiler_types.h:583:4: note: expanded from macro '__compiletime_assert' 583 | prefix ## suffix(); \ | ^ :319:1: note: expanded from here 319 | __compiletime_assert_2006 | ^ -- Jens Axboe