From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F0B8CC3B187 for ; Tue, 11 Feb 2020 18:34:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CCA6B2082F for ; Tue, 11 Feb 2020 18:34:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581446051; bh=LZkvVxuLaqcYosE8lpGU/19SJTjKBBWO1F+j8oX0KOA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=omTEp83DceAe31fTjWNBIBiufbdtf8aMiU/hmVijjgTelK6R/lAEIZpFjLphF3d/C ARx3K0gs4jtCFmd2LhJVPG0152r6mDqXulJMcuWrUtWUwwTLCPOBhy+de0Vker9HvO Slh1SzbVrOgHfYjCOJWCZzk+GPYowAoNcglcqOIo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730447AbgBKSeL (ORCPT ); Tue, 11 Feb 2020 13:34:11 -0500 Received: from mail.kernel.org ([198.145.29.99]:60564 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727361AbgBKSeK (ORCPT ); Tue, 11 Feb 2020 13:34:10 -0500 Received: from localhost (unknown [104.133.9.100]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 02286206D6; Tue, 11 Feb 2020 18:34:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581446050; bh=LZkvVxuLaqcYosE8lpGU/19SJTjKBBWO1F+j8oX0KOA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=M2M03d2olXiAMtg2enugDIdCtj2HkFcdNOYmXqITJKwXkSbp3s+ppzpLpRBXarylN cpipXTA/2F4uz80G8cfH0+myldr2adPBDVEZKllfQDsmiUJK9Cuc+iHZbvG1qkJ8pT ASXSFlIGNinPoj1/jM1I7MF4h0ZKfSRzYsck3sHE= Date: Tue, 11 Feb 2020 10:34:09 -0800 From: Greg KH To: Taehee Yoo Cc: rafael@kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v2] debugfs: Check module state before warning in {full/open}_proxy_open() Message-ID: <20200211183409.GB1938663@kroah.com> References: <20200206064757.10726-1-ap420073@gmail.com> <20200210214050.GA1579465@kroah.com> <20200211122819.GA1858119@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, Feb 12, 2020 at 02:18:38AM +0900, Taehee Yoo wrote: > On Tue, 11 Feb 2020 at 21:28, Greg KH wrote: > > > > Hi Greg! > > > On Tue, Feb 11, 2020 at 03:09:13PM +0900, Taehee Yoo wrote: > > > On Tue, 11 Feb 2020 at 06:40, Greg KH wrote: > > > > > > > > > > Hi Greg, > > > Thank you for your review! > > > > > > > On Thu, Feb 06, 2020 at 06:47:56AM +0000, Taehee Yoo wrote: > > > > > When the module is being removed, the module state is set to > > > > > MODULE_STATE_GOING. At this point, try_module_get() fails. > > > > > And when {full/open}_proxy_open() is being called, > > > > > it calls try_module_get() to try to hold module reference count. > > > > > If it fails, it warns about the possibility of debugfs file leak. > > > > > > > > > > If {full/open}_proxy_open() is called while the module is being removed, > > > > > it fails to hold the module. > > > > > So, It warns about debugfs file leak. But it is not the debugfs file > > > > > leak case. So, this patch just adds module state checking routine > > > > > in the {full/open}_proxy_open(). > > > > > > > > > > Test commands: > > > > > #SHELL1 > > > > > while : > > > > > do > > > > > modprobe netdevsim > > > > > echo 1 > /sys/bus/netdevsim/new_device > > > > > modprobe -rv netdevsim > > > > > done > > > > > > > > > > #SHELL2 > > > > > while : > > > > > do > > > > > cat /sys/kernel/debug/netdevsim/netdevsim1/ports/0/ipsec > > > > > done > > > > > > > > > > Splat looks like: > > > > > [ 298.766738][T14664] debugfs file owner did not clean up at exit: ipsec > > > > > [ 298.766766][T14664] WARNING: CPU: 2 PID: 14664 at fs/debugfs/file.c:312 full_proxy_open+0x10f/0x650 > > > > > [ 298.768595][T14664] Modules linked in: netdevsim(-) openvswitch nsh nf_conncount nf_nat nf_conntrack nf_defrag_ipv6 n][ 298.771343][T14664] CPU: 2 PID: 14664 Comm: cat Tainted: G W 5.5.0+ #1 > > > > > [ 298.772373][T14664] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006 > > > > > [ 298.773545][T14664] RIP: 0010:full_proxy_open+0x10f/0x650 > > > > > [ 298.774247][T14664] Code: 48 c1 ea 03 80 3c 02 00 0f 85 c1 04 00 00 49 8b 3c 24 e8 e4 b5 78 ff 84 c0 75 2d 4c 89 ee 48 > > > > > [ 298.776782][T14664] RSP: 0018:ffff88805b7df9b8 EFLAGS: 00010282[ 298.777583][T14664] RAX: dffffc0000000008 RBX: ffff8880511725c0 RCX: 0000000000000000 > > > > > [ 298.778610][T14664] RDX: 0000000000000000 RSI: 0000000000000006 RDI: ffff8880540c5c14 > > > > > [ 298.779637][T14664] RBP: 0000000000000000 R08: fffffbfff15235ad R09: 0000000000000000 > > > > > [ 298.780664][T14664] R10: 0000000000000001 R11: 0000000000000000 R12: ffffffffc06b5000 > > > > > [ 298.781702][T14664] R13: ffff88804c234a88 R14: ffff88804c22dd00 R15: ffffffff8a1b5660 > > > > > [ 298.782722][T14664] FS: 00007fafa13a8540(0000) GS:ffff88806c800000(0000) knlGS:0000000000000000 > > > > > [ 298.783845][T14664] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > > > > [ 298.784672][T14664] CR2: 00007fafa0e9cd10 CR3: 000000004b286005 CR4: 00000000000606e0 > > > > > [ 298.785739][T14664] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > > > > [ 298.786769][T14664] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > > > > [ 298.787785][T14664] Call Trace: > > > > > [ 298.788237][T14664] do_dentry_open+0x63c/0xf50 > > > > > [ 298.788872][T14664] ? open_proxy_open+0x270/0x270 > > > > > [ 298.789524][T14664] ? __x64_sys_fchdir+0x180/0x180 > > > > > [ 298.790169][T14664] ? inode_permission+0x65/0x390 > > > > > [ 298.790832][T14664] path_openat+0xc45/0x2680 > > > > > [ 298.791425][T14664] ? save_stack+0x69/0x80 > > > > > [ 298.791988][T14664] ? save_stack+0x19/0x80 > > > > > [ 298.792544][T14664] ? path_mountpoint+0x2e0/0x2e0 > > > > > [ 298.793233][T14664] ? check_chain_key+0x236/0x5d0 > > > > > [ 298.793910][T14664] ? sched_clock_cpu+0x18/0x170 > > > > > [ 298.794527][T14664] ? find_held_lock+0x39/0x1d0 > > > > > [ 298.795153][T14664] do_filp_open+0x16a/0x260 > > > > > [ ... ] > > > > > > > > > > Fixes: 9fd4dcece43a ("debugfs: prevent access to possibly dead file_operations at file open") > > > > > Reported-by: kbuild test robot > > > > > Signed-off-by: Taehee Yoo > > > > > --- > > > > > > > > > > v1 -> v2: > > > > > - Fix compile error > > > > > > > > > > fs/debugfs/file.c | 18 ++++++++++++++---- > > > > > 1 file changed, 14 insertions(+), 4 deletions(-) > > > > > > > > > > diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c > > > > > index 634b09d18b77..e3075389fba0 100644 > > > > > --- a/fs/debugfs/file.c > > > > > +++ b/fs/debugfs/file.c > > > > > @@ -175,8 +175,13 @@ static int open_proxy_open(struct inode *inode, struct file *filp) > > > > > if (r) > > > > > goto out; > > > > > > > > > > - real_fops = fops_get(real_fops); > > > > > - if (!real_fops) { > > > > > + if (!fops_get(real_fops)) { > > > > > +#ifdef MODULE > > > > > + if (real_fops->owner && > > > > > + real_fops->owner->state == MODULE_STATE_GOING) > > > > > + goto out; > > > > > +#endif > > > > > > > > Why is this in a #ifdef? > > > > > > > > The real_fops->owner field will be present if MODULE is not enabled, > > > > right? Shouldn't this just work the same for that case? > > > > > > > > > > The reason for the #ifdef is to avoid compile error > > > MODULE_STATE_GOING is defined if CONFIG_MODULES is enabled. > > > > We should fix that in the .h file where that is defined so that we don't > > have to mess with stuff like this in a .c file. > > > > > So, If the #ifdef doesn't exist, compile will errors. > > > But honestly, I'm not sure whether CONFIG_MODULES should be used > > > here instead of MODULE or not. > > > > Neither, #ifdefs shouldn't be in .c files :) > > > > Thank you for the review. > I would like to move MODULE_STATE_XXX flags to outside of CONFIG_MODULES. That would be good. > In addition, I think a new inline function, which checks modules state > would be helpful for this case. > The inline function code would like this. > > +static inline bool module_is_going(struct module *mod) > +{ > + return mod->state == MODULE_STATE_GOING; > +} That too would be good, as there are a number of places in the kernel that could be cleaned up to use this. Same for MODULE_STATE_COMING, right? So a patch series with all of this would be appreciated. thanks, greg k-h