Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752071AbcLLVRO (ORCPT ); Mon, 12 Dec 2016 16:17:14 -0500 Received: from mail-wm0-f49.google.com ([74.125.82.49]:36854 "EHLO mail-wm0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750813AbcLLVRM (ORCPT ); Mon, 12 Dec 2016 16:17:12 -0500 MIME-Version: 1.0 In-Reply-To: References: From: Dmitry Vyukov Date: Mon, 12 Dec 2016 22:16:50 +0100 Message-ID: Subject: Re: usb/core: warning in usb_create_ep_devs/sysfs_create_dir_ns To: Alan Stern Cc: Andrey Konovalov , Greg Kroah-Hartman , USB list , LKML , Kostya Serebryany , syzkaller Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1212 Lines: 27 On Mon, Dec 12, 2016 at 10:05 PM, Alan Stern wrote: > On Mon, 12 Dec 2016, Andrey Konovalov wrote: > >> Hi! >> >> While running the syzkaller fuzzer I've got the following error report. >> >> On commit 3c49de52d5647cda8b42c4255cf8a29d1e22eff5 (Dev 2). >> >> WARNING: CPU: 2 PID: 865 at fs/sysfs/dir.c:31 sysfs_warn_dup+0x8a/0xa0 >> gadgetfs: disconnected >> sysfs: cannot create duplicate filename >> '/devices/platform/dummy_hcd.0/usb2/2-1/2-1:64.0/ep_05' >> Kernel panic - not syncing: panic_on_warn set ... > > I suppose we could check for USB devices that claim to have two > endpoints with the same address. But is it really worthwhile? A > kernel warning isn't so bad when you're dealing with buggy device > firmware. We need a clear distinction between what is a bug in kernel source code and what is incorrect user-space code. Otherwise no automated testing is possible. WARNING means bug in kernel source code. If it is not a bug in kernel source code, then it must not produce a WARNING. If it's a condition that we absolutely need to make user-space aware of, then we can print a single line with an explanation to console (but not prefixed with "WARNING:" nor "BUG:").