From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9B30C1AF0BB; Thu, 30 Jul 2026 14:25:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785421556; cv=none; b=TWbrOeZCdBRXAzJ9/9vU8204iXcHriHvZIg3Wwx+ZRWpTLqyuWWjmVfjdG6VhqQOiCUCrAu0HqG6n8BpMXDdCUaumuNv56lr/z5PSdFBXrlSxFvEAXrNKYZf+0wkXBtFZCn0hWy4HZgFnLvJ5K/IDSO+Gs+Wf8TpjKaFxVhY1c0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785421556; c=relaxed/simple; bh=Y8oG0rDmEXqsbCTu17Gg3ptE3e/jNI6oGxIPdznHQcA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=H58dJcKNkpsCJoGC8efk2NRgnkTb5EfcRaNqVS6XnN31AzQTk9cKAosUi4R0vZ76/tnb/G3E1N6BXlPFI883xg+kzpRedCq5XEQQCL6y5QswAcjwhwA0cBnYs6h/XmdG9K5LLfbwBelAv4B5nXriK9vR2xL0WPNYoeCfLUqr/NQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ZC/6Z5qF; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="ZC/6Z5qF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 01BF81F00A3A; Thu, 30 Jul 2026 14:25:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785421554; bh=wfIZZrWrvimCDoZP1I1TtveBY1x58nV8eM0ou8yy+es=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ZC/6Z5qFV2Heo4s+o3M0K/jVH3YJC6LmQsyAgW+Cz/IyUn0BZLuP/O68zR1MJYW42 Cc0SBJ1jFJDPRQrv/hMRJ1hoG43+WO4SQlFNT+rAYFcSJex5Q0899uyiudEi6vFM3A zM/6QxZxI4OCiV1nsrIeZg0ZrqfhSql6FfKhszLM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable , Fan Wu Subject: [PATCH 7.1 144/744] usb: gadget: f_midi: cancel pending IN work before freeing the midi object Date: Thu, 30 Jul 2026 16:06:57 +0200 Message-ID: <20260730141447.348552659@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260730141444.267951807@linuxfoundation.org> References: <20260730141444.267951807@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Fan Wu commit 5650c18d93a1db7e27cb5a40b394747eb4686d5b upstream. The f_midi driver embeds a work item (midi->work) whose handler, f_midi_in_work(), dereferences the enclosing struct f_midi through container_of(). This work is armed from two sites: f_midi_complete(), on a normal IN-endpoint completion, and f_midi_in_trigger(), on an ALSA rawmidi output-stream start. Neither f_midi_disable() nor f_midi_unbind() cancels midi->work. f_midi_disable() only disables the endpoints and drains the in_req_fifo; it does not synchronize the work item, and the sound card is released asynchronously to the final free of the midi object. The midi object is reference-counted (midi->free_ref) and is freed in f_midi_free() only once both the usb_function reference and the rawmidi private_data reference have been dropped. In f_midi_unbind(), f_midi_disable() runs before the sound card is released, so while the USB endpoints are already disabled the rawmidi device is still usable by an open substream. A concurrent userspace write on such a substream can reach f_midi_in_trigger() and queue midi->work again after f_midi_disable() has returned. A work item armed this way may still be pending when the last reference drops and f_midi_free() proceeds to kfree(midi), letting f_midi_in_work() dereference the struct after it has been freed, a use-after-free. For this reason cancelling midi->work in f_midi_disable() would not be sufficient: the ALSA trigger path can rearm the work after disable() returns. Cancelling at the refcount-zero free site is the boundary after which neither arming source can survive, because by then both references that keep the midi object alive have been dropped: the USB endpoints are already disabled and the rawmidi device has been released. Fix this by calling cancel_work_sync(&midi->work) in the refcount-zero block of f_midi_free(), before the embedded work_struct is freed along with the rest of the structure. opts->lock is a sleeping mutex, so calling cancel_work_sync() under it is permitted, and the handler takes midi->transmit_lock rather than opts->lock, so no self-deadlock can occur while it waits for a running instance of the work to finish. This issue was found by an in-house static analysis tool. Fixes: 8653d71ce3763 ("usb/gadget: f_midi: Replace tasklet with work") Cc: stable Assisted-by: Codex:gpt-5.5 Signed-off-by: Fan Wu Link: https://patch.msgid.link/20260709150717.399083-1-fanwu01@zju.edu.cn Signed-off-by: Greg Kroah-Hartman --- drivers/usb/gadget/function/f_midi.c | 1 + 1 file changed, 1 insertion(+) --- a/drivers/usb/gadget/function/f_midi.c +++ b/drivers/usb/gadget/function/f_midi.c @@ -1309,6 +1309,7 @@ static void f_midi_free(struct usb_funct opts = container_of(f->fi, struct f_midi_opts, func_inst); mutex_lock(&opts->lock); if (!--midi->free_ref) { + cancel_work_sync(&midi->work); kfree(midi->id); kfifo_free(&midi->in_req_fifo); kfree(midi);