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[119.74.6.224]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3965547159asm1916964a91.12.2026.08.25.03.31.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Aug 2026 03:31:48 -0700 (PDT) From: Wei Jie Law <98lawweijie@gmail.com> To: Jiri Kosina , Benjamin Tissoires Cc: Andrew Duggan , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH v2] HID: rmi: fix use-after-free of struct rmi_data via reset_work Date: Tue, 25 Aug 2026 18:31:44 +0800 Message-ID: <20260825103144.12356-1-98lawweijie@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-input@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit rmi_event() queues hdata->reset_work for any pointer/mouse usage as soon as RMI_DEVICE is set, but rmi_remove() only cancels the work when RMI_STARTED is set: if ((hdata->device_flags & RMI_DEVICE) && test_bit(RMI_STARTED, &hdata->flags)) { clear_bit(RMI_STARTED, &hdata->flags); cancel_work_sync(&hdata->reset_work); rmi_unregister_transport_device(&hdata->xport); } RMI_STARTED is set at the very end of rmi_input_configured(), so a device that advertises the RMI report IDs - which is what makes rmi_probe() set RMI_DEVICE - but then makes rmi_input_configured() fail leaves the work schedulable and never cancelled. Never answering the SET_REPORT that rmi_set_mode() issues is enough, i.e. exactly the unreachable-device case the guard was added for. rmi_probe() still returns 0 there, because hidraw claims the device, so the driver stays bound and rmi_event() keeps running. struct rmi_data is devm_kzalloc()'d on &hdev->dev, so hid_device_remove() releases it as soon as ->remove() returns, with the work still queued or still running. The workqueue then reads and writes the freed object: process_one_work() stores into work->data, list_del_init()s work->entry, and loads work->func out of freed memory before calling it, while rmi_reset_work() dereferences hdata->hdev, which the same unplug freed. BUG: KASAN: slab-use-after-free in process_one_work+0xd96/0x10b0 Read of size 8 at addr ffff8881095c0540 by task kworker/0:4/3058 [...] Allocated by task 450: devm_kmalloc+0x7c/0x220 rmi_probe+0x36/0xcf0 [hid_rmi] hid_device_probe+0x286/0x430 Freed by task 9278: kfree+0x125/0x420 release_nodes+0xf0/0x260 devres_release_group+0x23a/0x3a0 hid_device_remove+0xf5/0x220 The read is of hdata->reset_work.func, 320 bytes into the freed 512-byte region, which process_one_work() calls straight afterwards. Without KASAN the same reproducer oopses in rmi_reset_work() and leaves the kworker "exited with irqs disabled". Cancel the work unconditionally in rmi_remove(), and do not queue it before rmi_input_configured() has succeeded or after rmi_remove() has cleared RMI_STARTED. A report can still pass the RMI_STARTED test in rmi_event() just before rmi_remove() clears the bit and queue the work after that cancel, so cancel once more after hid_hw_stop() has stopped the report flow, and make rmi_reset_work() bail out when RMI_STARTED is clear - by then the transport device it would reset has been unregistered. Fixes: 8725aa4fa7de ("HID: rmi: Check that the RMI_STARTED bit is set before unregistering the RMI transport device") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-5 Assisted-by: GLM:glm-5.3 Signed-off-by: Wei Jie Law <98lawweijie@gmail.com> --- Changes in v2: - No code change: the diff is identical to v1. Adds the Assisted-by tags required by Documentation/process/coding-assistants.rst. This is independent of the pending "HID: rmi: fix OOB access with undersized RMI reports" [1] (whose v5, also a tags-only respin, is being sent alongside this) -- they touch different functions, and either order applies cleanly. They are worth taking together, though. That patch makes a zero-length READ_DATA reply fail rmi_hid_read_block() with -EIO instead of spinning in it, so rmi_scan_pdt(), and hence rmi_input_configured(), now fail where they previously hung with the device lock held. That failure leaves RMI_DEVICE set and RMI_STARTED clear -- the state this patch is about -- and, because the probe no longer hangs, it also lets the unplug that triggers the use-after-free complete. The route described above, never answering the SET_REPORT that rmi_set_mode() issues, reaches the same state on an unpatched tree, so this is not a regression from that patch; it is a second way in, and an argument for the two landing in the same release. [1] https://lore.kernel.org/all/20260825060954.104890-1-98lawweijie@gmail.com/ v1: https://lore.kernel.org/linux-input/20260825034854.63555-1-98lawweijie@gmail.com/ drivers/hid/hid-rmi.c | 40 ++++++++++++++++++++++++++++++++++------ 1 file changed, 34 insertions(+), 6 deletions(-) diff --git a/drivers/hid/hid-rmi.c b/drivers/hid/hid-rmi.c index d4af17fdba46..13a301404ff8 100644 --- a/drivers/hid/hid-rmi.c +++ b/drivers/hid/hid-rmi.c @@ -313,6 +313,14 @@ static void rmi_reset_work(struct work_struct *work) struct rmi_data *hdata = container_of(work, struct rmi_data, reset_work); + /* + * A report that raced with rmi_remove() may have queued us after it + * cleared RMI_STARTED, i.e. after the transport device we would reset + * has been unregistered. + */ + if (!test_bit(RMI_STARTED, &hdata->flags)) + return; + /* switch the device to RMI if we receive a generic mouse report */ rmi_reset_attn_mode(hdata->hdev); } @@ -412,7 +420,13 @@ static int rmi_event(struct hid_device *hdev, struct hid_field *field, return 1; } - schedule_work(&data->reset_work); + /* + * Only reset a device that finished rmi_input_configured(); + * before that, and after rmi_remove() has cleared the bit, + * struct rmi_data may go away under the work. + */ + if (test_bit(RMI_STARTED, &data->flags)) + schedule_work(&data->reset_work); return 1; } @@ -739,15 +753,29 @@ static int rmi_probe(struct hid_device *hdev, const struct hid_device_id *id) static void rmi_remove(struct hid_device *hdev) { struct rmi_data *hdata = hid_get_drvdata(hdev); + bool started = test_and_clear_bit(RMI_STARTED, &hdata->flags); - if ((hdata->device_flags & RMI_DEVICE) - && test_bit(RMI_STARTED, &hdata->flags)) { - clear_bit(RMI_STARTED, &hdata->flags); - cancel_work_sync(&hdata->reset_work); + /* + * reset_work lives inside the devm-allocated hdata, which is freed as + * soon as this returns, so it has to be cancelled whether or not the + * device ever reached the RMI_STARTED state. Cancel it here, while + * the transport device it resets is still registered. + */ + cancel_work_sync(&hdata->reset_work); + + if ((hdata->device_flags & RMI_DEVICE) && started) rmi_unregister_transport_device(&hdata->xport); - } hid_hw_stop(hdev); + + /* + * A report that passed the RMI_STARTED test in rmi_event() just before + * the clear above can queue the work again after that first cancel. + * Such a work item does nothing, but it still has to be reaped before + * hdata goes away. hid_hw_stop() has stopped the report flow, so no + * further queueing is possible by now. + */ + cancel_work_sync(&hdata->reset_work); } static const struct hid_device_id rmi_id[] = { -- 2.43.0