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Wed, 27 Aug 2025 15:23:29 -0700 (PDT) Message-ID: <7ac936ab-ff4f-457c-a745-56bccaa19a08@kernel.dk> Date: Wed, 27 Aug 2025 16:23:28 -0600 Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] io_uring/kbuf: fix infinite loop in io_kbuf_inc_commit() To: Keith Busch Cc: Qingyue Zhang , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, Suoxing Zhang References: <20250827114339.367080-1-chunzhennn@qq.com> <4b8eb795-239f-4f46-af4f-7a05056ab516@kernel.dk> Content-Language: en-US From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/27/25 3:59 PM, Keith Busch wrote: > On Wed, Aug 27, 2025 at 03:45:28PM -0600, Jens Axboe wrote: >>> + buf_len = READ_ONCE(buf->len); >>> + this_len = min_t(int, len, buf_len); >>> + buf_len -= this_len; >>> + if (buf_len) { >>> buf->addr += this_len; >>> + buf->len = buf_len; >>> return false; >>> } >>> + buf->len = 0; > > Purely for symmetry, assigning buf->len ought to be a WRITE_ONCE. I did think about that, perhaps I should've mentioned it in the commit message. While the reader side is important for the reasons stated, the updating of buf->len isn't really as only the serialized kernel side will do it. Hence the WRITE_ONCE() should not be needed on the write side, outside of perhaps documenting that this is a shared buffer. -- Jens Axboe