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Tue, 19 Aug 2025 09:00:36 -0700 (PDT) Message-ID: <1155b8b0-d5d0-4634-984b-71d246932af7@kernel.dk> Date: Tue, 19 Aug 2025 10:00:36 -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 V3] io_uring: uring_cmd: add multishot support To: Ming Lei , io-uring@vger.kernel.org, Pavel Begunkov Cc: Caleb Sander Mateos References: <20250819150040.980875-1-ming.lei@redhat.com> From: Jens Axboe Content-Language: en-US In-Reply-To: <20250819150040.980875-1-ming.lei@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/19/25 9:00 AM, Ming Lei wrote: > @@ -251,6 +265,11 @@ int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags) > } > > ret = file->f_op->uring_cmd(ioucmd, issue_flags); > + if (ioucmd->flags & IORING_URING_CMD_MULTISHOT) { > + if (ret >= 0) > + return IOU_ISSUE_SKIP_COMPLETE; > + io_kbuf_recycle(req, issue_flags); > + } > if (ret == -EAGAIN) { > ioucmd->flags |= IORING_URING_CMD_REISSUE; > return ret; Final comment on this part... uring_cmd is unique in the sense that it'd be the first potentially pollable file type that supports buffer selection AND can return -EIOCBQUEUED. For non-pollable, the buffer would get committed upfront. For pollable, we'd either finish and put it within this same execution context, or we'd drop it entirely when returning -EAGAIN. So what happens if we get -EIOCBQUEUED with a selected buffer from provided buffer ring, and someome malicious unregisters and frees the buffer ring before that request completes? -- Jens Axboe