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 674E13AFD16; Mon, 17 Aug 2026 14:26:22 +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=1786976784; cv=none; b=hmUdCUNvepR+oTo25f1N13f0VWa9U87qK/kuoQi6en4r5a8XwWMkBN+ftu2rLiccKibOLysXcmBO1wYtS1GrchH6c7hJMB1iEQ1dI5lNwwqN1qwVUQ6hEc6iGZRfQmxwrDwlCoZs04Fm/VbKjzbLpx0KSsRIEIX5JvfdmR8/Kvw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786976784; c=relaxed/simple; bh=1lgJTNPIhjgQfhFuSEWam4BcfY44QKZD7DMyF4Su82Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=OFjams3CH6/3/mwmz/fwYIaz8zi/SkglmqKOzVMp7pjdH4IzXosn3KLl50YcmWFxW64UvGwj0gpnqDFOof/hjQa51yKgsEqH1JI4fra0siCJiQZVnXOVZ4B+0qgKNNV9AioW7lnqrCLQnqS8DiObA87AYwtPhVD8P0wuw+eHs2I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=vu3l1wSd; 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="vu3l1wSd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C073E1F000E9; Mon, 17 Aug 2026 14:26:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786976782; bh=z0ay/IsE6dfR3c4GMA+pi1xI5TI69VWyu7bc6gDw7yo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=vu3l1wSd6+qUKoATurCGY74JneUqX3trO2B3WCoB9i+JJ+ESSIqtzDyp0uxARL5F8 fIliUrAPvrPk5HZSgguOrqiboKUQRvHrFAxkR0RviO+ZquJWwMggjb5PIzquEi2NQT +BjgBzTMpB+axi/JlU+hCW7Vr6As9qAczxwAqjRg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable , Fan Wu Subject: [PATCH 5.15 063/456] usb: gadget: f_midi: cancel pending IN work before freeing the midi object Date: Mon, 17 Aug 2026 15:27:33 +0200 Message-ID: <20260817132542.511654295@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260817132539.792407575@linuxfoundation.org> References: <20260817132539.792407575@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 5.15-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 @@ -1258,6 +1258,7 @@ 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);