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Fri, 01 May 2026 14:42:06 -0700 (PDT) Message-ID: <74e3db05-780a-4a2d-9e54-63a4f00decca@kernel.dk> Date: Fri, 1 May 2026 15:42:05 -0600 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 5.10 491/491] io_uring/poll: correctly handle io_poll_add() return value on update To: Sasha Levin Cc: Ben Hutchings , Greg Kroah-Hartman , stable@vger.kernel.org, patches@lists.linux.dev, syzbot+641eec6b7af1f62f2b99@syzkaller.appspotmail.com, lvc-project@linuxtesting.org, Fedor Pchelkin References: <20260413155819.042779211@linuxfoundation.org> <20260501111233-b371eac52cd006bfddfbd9e5-pchelkin@ispras> <20260501200000.item005-revert@kernel.org> <6eb47d20-ed49-45f6-90f1-41c15fa99896@kernel.dk> Content-Language: en-US From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/1/26 3:39 PM, Sasha Levin wrote: > On Fri, May 01, 2026 at 03:23:33PM -0600, Jens Axboe wrote: >> On 5/1/26 3:11 PM, Sasha Levin wrote: >>> On Fri, 01 May 2026 11:54:18 +0300, Fedor Pchelkin wrote: >>>> The Fixes: tag of upstream 84230ad2d2afb points to 97b388d70b53 >>>> ("io_uring: handle completions in the core", v5.19), which is NOT >>>> present in 5.10 or 5.15. Additionally, in 5.10/5.15 'preq->result' >>>> is unsigned so the 'if (preq->result < 0)' check is a no-op, and >>>> __io_poll_add() already completes the request when it returns >>>> non-zero, leading to a potential double-completion. >>>> >>>> I would suggest to revert the patch from these trees because there >>>> appears to be no real bug to fix. >>> >>> Agreed. I've reverted both the original backport and the followup >>> "fix backport" commit on 5.10 and 5.15. >> >> Please hold off, I have fully tested these. It's quite possible they are >> wonky in certain ways, but they currently fix a livelock as well that >> you can hit on 5.10/15 which is arguably worse. Double claim + complete >> should be handled by the poll grab side, I'm _assuming_ more cosmetic >> than anything else. >> >> Please refrain from dropping patches until they have been confirmed by >> someone that actually knows the code. I've been busy today and haven't >> had time to look into this one just yet. You're just making more work >> for me by dropping this you have little insight into. > > I haven't realized that this was a custom backport - I thought that they were > pulled in without the Fixes commit being present. > > I'll drop the revert, luckily this wasn't pushed to stable-queue yet. Please just add the fixup, which should go into 5.15-stable as well of course. Both of those have been notified about previously. -- Jens Axboe