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 5CD0630C618; Thu, 30 Jul 2026 15:02:10 +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=1785423732; cv=none; b=UjKJtDYCGZSN1pf5IriniE4EeJ9PD0qoN6aoHBN2hTfpQuOHicDbJ9p+uW5/SlilJHIatE+6rPTcC/tKWdRv5+av9crTKwLoKMMgqujx6pQoMgoT4E9Yryfxix4tmJlBu9399L2MepiSId9DFeUn9zOd8WTxJQtmZh8W7V8wjHg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785423732; c=relaxed/simple; bh=dd8i60R3D4ha5j9rK6oLQLY3WsfutlE9MnL1XsnUNwc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=bAvwar0rpK6RrC1ZVuuHCatGigXCOFM4O0yJOdY0pLkeVEYV5lZ5M3rpVfmzamdxlhqSIW7W+LMq0563hqV2MAMVnXiA3W9np7dXnvaJ24Vd4z6pRrx2WOplV/smqGY711KAF6jKeU03KmzdflDxr48oDFGmhmZXwOhSke6vgLQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=XhxpHCGS; 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="XhxpHCGS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B7E681F000E9; Thu, 30 Jul 2026 15:02:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785423730; bh=CB4xrWsn54JkG5cDeZfvlzxc0UtAfkgPMM2zSJz7OWA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=XhxpHCGSFETpLhp9zMWteeQCHAculwoamHGztj4TUH88ZKfGsnXAPy9rnNi/xv26s pMTeoXqbzGecSPqxm9dBigPcMIC9HqxbGVOp0AqOIQeIV/eoUL5J/sI0xA7GEbD4Pq mGMGKB6i54vFICW6SiX9kZ41tMTqB52+jD/OvhQw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable , Fan Wu Subject: [PATCH 6.18 146/675] usb: gadget: f_midi: cancel pending IN work before freeing the midi object Date: Thu, 30 Jul 2026 16:07:56 +0200 Message-ID: <20260730141448.241478435@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260730141445.110192266@linuxfoundation.org> References: <20260730141445.110192266@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 6.18-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 @@ -1302,6 +1302,7 @@ 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);