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Fri, 04 Sep 2026 09:14:26 -0700 (PDT) Received: from archlinux.lan ([136.34.156.120]) by smtp.gmail.com with ESMTPSA id 006d021491bc7-6b6dd07214bsm3597912eaf.10.2026.09.04.09.14.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Sep 2026 09:14:25 -0700 (PDT) From: Danish Khateeb To: Jiri Kosina , Benjamin Tissoires Cc: linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, sashiko-reviews@lists.linux.dev, Danish Khateeb Subject: Re: [PATCH] HID: corsair: cancel worker after unregistering LED, not before Date: Fri, 4 Sep 2026 11:13:54 -0500 Message-ID: <20260904161354.159922-1-danishkhateeb03@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904145330.BD9E41F00A3D@smtp.kernel.org> References: <20260904143610.119808-1-danishkhateeb03@gmail.com> <20260904145330.BD9E41F00A3D@smtp.kernel.org> Precedence: bulk X-Mailing-List: linux-input@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit > - [High] Reordering `led_classdev_unregister()` before > `cancel_work_sync()` reintroduces a Time-of-Check to Time-of-Use > (TOCTOU) Use-After-Free race condition on `led->cdev.dev` inside the > worker threads. You are right. Please drop v1. There are two races here and each ordering fixes only one. Cancelling first leaves led_classdev_unregister() free to re-arm the worker via led_set_brightness(LED_OFF), so the structure is freed while still linked into the worklist. Cancelling last leaves a worker that has already tested led->removed free to dereference led->cdev.dev after device_unregister() has freed it -- the race eb51c9f8cb4f fixed. v1 was in effect a revert of it, which I should have caught: that race is spelled out in the changelog of the commit in my own Fixes: tag. v2 uses disable_work_sync(), which waits for a running worker and makes the later schedule_work() fail rather than queue, closing both. It also converts the fail_sysfs error path, which still had the second race. My reproducer only covered the re-arm race; the other is a few instructions wide and I could not trigger it. v2 says so.