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[185.147.214.8]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48a8ebb3dc1sm46220865e9.14.2026.05.01.03.36.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 01 May 2026 03:36:48 -0700 (PDT) Date: Fri, 1 May 2026 18:36:42 +0800 From: Ming Lei To: Jens Axboe Cc: linux-block@vger.kernel.org, Caleb Sander Mateos , Uday Shankar Subject: Re: [PATCH] ublk: reject FETCH from non-userspace context Message-ID: References: <20260501085216.905401-1-tom.leiming@gmail.com> <9efbd035-b40e-4155-8382-b42acff75a9e@kernel.dk> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9efbd035-b40e-4155-8382-b42acff75a9e@kernel.dk> On Fri, May 01, 2026 at 04:34:11AM -0600, Jens Axboe wrote: > On 5/1/26 2:52 AM, Ming Lei wrote: > > __ublk_fetch() sets io->task to current, which is later checked > > against io_uring_cmd_get_task() in ublk_uring_cmd_cancel_fn(). > > With REQ_F_FORCE_ASYNC, the FETCH uring_cmd can be issued from > > task work, which can be run from io_uring's fallback workqueue, > > causing a task mismatch and triggering the WARN in cancel_fn. > > > > Reject FETCH if current is not a real userspace task, and it is > > reasonable for failing it in case of io_uring fallback. > > I think this should be caught in ublk_ch_uring_cmd_cb(), which > should not hit ublk_ch_uring_cmd_local() if tw.cancel is true. > fallback work should just be terminated, not be issued. Yeah, that is definitely better, will take it in V2. Thanks, Ming