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 6DB0C443A92; Thu, 30 Jul 2026 15:33:03 +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=1785425585; cv=none; b=qL6bZBnLiaz7JqOe+67f2rrbZNDa1cmy3imtSSeTc7ob/TOlHLcu9QwJK3uxfvsNf4tHaQtON40kLzS1FvyhCg8NK3aTyiMKEwxGNBogwWPxNNYPmx8SoytYF9DXIkVrJYn7pakzbg7PDPS75l/KgQA1zzqWiE+6HAt/KfFGonk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785425585; c=relaxed/simple; bh=GTZ7ZoIqnw7o6AJWofjM5Zmui/buR6uTqBfSC1BK3yQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=gBIM/dBd/IuvyxPZeIK14O0Uyl9rW8p7IyD+Lxa6AibB+SptFh6mqezcgDQL1tbCQf6PHiHt08JSWbfG4q+uNSwtjGV4LoDcxfsBzHa00lG4gDZ1ItNfg4eYPB8pKt2aKQP5qNmySt8YaeeogXwzQkBzkHEi52oyma8B/lB+/Zw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=F9qfD5md; 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="F9qfD5md" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F32861F000E9; Thu, 30 Jul 2026 15:33:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785425583; bh=IJh3almZgu4DBNEZ1md5TWoHoN0fWhpRPwJSKRY5Tws=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=F9qfD5mdfdU+TNQ6mEfe1PzEZNijZe6Wn/yCyiyc2py5JoWTihgegDa404kSsBTQt PvO3fhzX/c9JFWlU/yRdtRYpWXkPZXFDCz7REDOSciJaeuiTWF/7A9H2MuXRq79wEa X4yz4ruRzSWmNDL60GF1DwVdY0DhXFQn+yu23Sk0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable , Fan Wu Subject: [PATCH 6.12 119/602] usb: gadget: f_midi: cancel pending IN work before freeing the midi object Date: Thu, 30 Jul 2026 16:08:31 +0200 Message-ID: <20260730141438.489127598@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260730141435.976815864@linuxfoundation.org> References: <20260730141435.976815864@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 6.12-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);