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Fri, 28 Aug 2026 07:32:18 -0700 (PDT) Date: Fri, 28 Aug 2026 07:32:14 -0700 From: Dmitry Torokhov To: Jeffin Philip Cc: linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+1e2ef9bcb29af666b2e6@syzkaller.appspotmail.com Subject: Re: [PATCH v2] Input: atkbd - fix UAF in atkbd_set_repeat_rate() on disconnect Message-ID: References: <20260828100547.120553-1-jeffinphilip14@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@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: <20260828100547.120553-1-jeffinphilip14@gmail.com> Hi Jeffin, On Fri, Aug 28, 2026 at 03:35:47PM +0530, Jeffin Philip wrote: > Commit 0ef7a26af127 ("Input: atkbd - fix canceling event_work in disconnect") > moved cancel_delayed_work_sync() after input_unregister_device() on > the premise that events may arrive until input_unregister_device returns. > > However, this created a UAF as work that may have passed the > atkbd->enabled check in atkbd_event_work() may attempt to dereference dev > which is freed in input_unregister_device(). Reverting the commit also > does not solve the issue as events may still come through and pass the > enabled check as atkbd_disable() and event_work() guard with different > locks. Fix this by closing the hardware first using serio_close() > and then unregistering to prevent work from executing after > input_unregister_device(). serio_close() closes the device preventing > work from arriving. Additionally add a check for atkbd->enabled in > atkbd_event() to prevent userspace from queuing new events after > atkbd_disable() sets atkbd->enabled to false. I believe the proper fix is to replace cancel_delayed_work_sync() with disable_delayed_work_sync() to prevent rescheduling due to atkbd being marked as disabled. Thanks. -- Dmitry