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([2607:fb90:bdd1:e0ac:ec4b:d50b:ac50:163c]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2de8f6615d5sm6453231eec.24.2026.04.15.18.50.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 15 Apr 2026 18:50:55 -0700 (PDT) Message-ID: Date: Wed, 15 Apr 2026 18:50:53 -0700 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 1/1] io_uring/poll: fix signed comparison in io_poll_get_ownership() To: Jens Axboe , Ren Wei , io-uring@vger.kernel.org Cc: asml.silence@gmail.com, yifanwucs@gmail.com, tomapufckgml@gmail.com, bird@lzu.edu.cn, zcliangcn@gmail.com, ylong030@ucr.edu References: <3a3508b08bcd7f1bc3beff848ae6e1d73d355043.1775965597.git.ylong030@ucr.edu> <6dc4f9dd-975b-436f-889b-7c584bc18e62@kernel.dk> Content-Language: en-US From: Yuan Tan In-Reply-To: <6dc4f9dd-975b-436f-889b-7c584bc18e62@kernel.dk> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 4/15/26 13:09, Jens Axboe wrote: > On 4/12/26 2:38 AM, Ren Wei wrote: >> From: Longxuan Yu >> >> io_poll_get_ownership() uses a signed comparison to check whether >> poll_refs has reached the threshold for the slowpath: >> >> if (unlikely(atomic_read(&req->poll_refs) >= IO_POLL_REF_BIAS)) >> >> atomic_read() returns int (signed). When IO_POLL_CANCEL_FLAG >> (BIT(31)) is set in poll_refs, the value becomes negative in >> signed arithmetic, so the >= 128 comparison always evaluates to >> false and the slowpath is never taken. >> >> Fix this by casting the atomic_read() result to unsigned int >> before the comparison, so that the cancel flag is treated as a >> large positive value and correctly triggers the slowpath. >> >> Fixes: aa43477b0402 ("io_uring: poll rework") > Is this correct? Seems it should be: > > Fixes: a26a35e9019f ("io_uring: make poll refs more robust") > I just double check it. Yes we were wrong. Correct bug inducing commit is  a26a35e9019f ("io_uring: make poll refs more robust"). Thanks for pointing it out. Do we need to send a v2 to fix this?