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Fri, 28 Aug 2026 03:06:03 -0700 (PDT) Received: from Default ([2409:40f4:1018:6686:df4d:699c:e13c:43d2]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-142e41837c6sm1910157c88.11.2026.08.28.03.06.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Aug 2026 03:06:03 -0700 (PDT) From: Jeffin Philip To: dmitry.torokhov@gmail.com Cc: linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, Jeffin Philip , syzbot+1e2ef9bcb29af666b2e6@syzkaller.appspotmail.com Subject: [PATCH v2] Input: atkbd - fix UAF in atkbd_set_repeat_rate() on disconnect Date: Fri, 28 Aug 2026 15:35:47 +0530 Message-ID: <20260828100547.120553-1-jeffinphilip14@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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. Reported-by: syzbot+1e2ef9bcb29af666b2e6@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=1e2ef9bcb29af666b2e6 Fixes: 0ef7a26af127 ("Input: atkbd - fix canceling event_work in disconnect") Signed-off-by: Jeffin Philip --- Changelog: - Changes in v2: Added a check for atkbd->enabled so userspace cannot queue events after atkbd_disable. Link to v1: https://lore.kernel.org/all/20260828080839.116065-1-jeffinphilip14@gmail.com/T/#u --- drivers/input/keyboard/atkbd.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/drivers/input/keyboard/atkbd.c b/drivers/input/keyboard/atkbd.c index 5736f4bc5a50..79e4cd9ee1db 100644 --- a/drivers/input/keyboard/atkbd.c +++ b/drivers/input/keyboard/atkbd.c @@ -672,6 +672,9 @@ static int atkbd_event(struct input_dev *dev, if (!atkbd->write) return -1; + if (!atkbd->enabled) + return -1; + switch (type) { case EV_LED: atkbd_schedule_event_work(atkbd, ATKBD_LED_EVENT_BIT); @@ -963,17 +966,18 @@ static void atkbd_disconnect(struct serio *serio) atkbd_disable(atkbd); - input_unregister_device(atkbd->dev); - /* - * Make sure we don't have a command in flight. - * Note that since atkbd->enabled is false event work will keep - * rescheduling itself until it gets canceled and will not try - * accessing freed input device or serio port. + * close serio first so device will not get any data, which prevents + * atkbd_event_work from being rescheduled after cancel_delayed_work_sync + * returns. This ensures no work can dereference atkbd->dev after it has + * been freed. */ - cancel_delayed_work_sync(&atkbd->event_work); serio_close(serio); + cancel_delayed_work_sync(&atkbd->event_work); + + input_unregister_device(atkbd->dev); + serio_set_drvdata(serio, NULL); kfree(atkbd); } -- 2.55.0