From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f72.google.com (mail-pl0-f72.google.com [209.85.160.72]) by kanga.kvack.org (Postfix) with ESMTP id 0445B6B0003 for ; Mon, 9 Apr 2018 22:39:18 -0400 (EDT) Received: by mail-pl0-f72.google.com with SMTP id 91-v6so8303814pla.18 for ; Mon, 09 Apr 2018 19:39:17 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id g1-v6sor750290pld.86.2018.04.09.19.39.16 for (Google Transport Security); Mon, 09 Apr 2018 19:39:17 -0700 (PDT) Date: Tue, 10 Apr 2018 11:39:10 +0900 From: Minchan Kim Subject: Re: [PATCH] mm: workingset: fix NULL ptr dereference Message-ID: <20180410023910.GC214542@rodete-desktop-imager.corp.google.com> References: <20180409024925.GA21889@bombadil.infradead.org> <20180409030930.GA214930@rodete-desktop-imager.corp.google.com> <20180409111403.GA31652@bombadil.infradead.org> <20180409112514.GA195937@rodete-laptop-imager.corp.google.com> <7706245c-2661-f28b-f7f9-8f11e1ae932b@huawei.com> <20180409144958.GA211679@rodete-laptop-imager.corp.google.com> <20180409152032.GB11756@bombadil.infradead.org> <20180409230409.GA214542@rodete-desktop-imager.corp.google.com> <20180410011211.GA31282@bombadil.infradead.org> <20180410023339.GB214542@rodete-desktop-imager.corp.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180410023339.GB214542@rodete-desktop-imager.corp.google.com> Sender: owner-linux-mm@kvack.org List-ID: To: Matthew Wilcox Cc: Chao Yu , Jaegeuk Kim , Christopher Lameter , Andrew Morton , linux-mm , LKML , Johannes Weiner , Jan Kara , Chris Fries , linux-f2fs-devel@lists.sourceforge.net, linux-fsdevel@vger.kernel.org On Tue, Apr 10, 2018 at 11:33:39AM +0900, Minchan Kim wrote: > On Mon, Apr 09, 2018 at 06:12:11PM -0700, Matthew Wilcox wrote: > > On Tue, Apr 10, 2018 at 08:04:09AM +0900, Minchan Kim wrote: > > > On Mon, Apr 09, 2018 at 08:20:32AM -0700, Matthew Wilcox wrote: > > > > I don't think this is something the radix tree should know about. > > > > > > Because shadow entry implementation is hidden by radix tree implemetation. > > > IOW, radix tree user cannot know how it works. > > > > I have no idea what you mean. > > > > > > SLAB should be checking for it (the patch I posted earlier in this > > > > > > I don't think it's right approach. SLAB constructor can initialize > > > some metadata for slab page populated as well as page zeroing. > > > However, __GFP_ZERO means only clearing pages, not metadata. > > > So it's different semantic. No need to mix out. > > > > No, __GFP_ZERO is specified to clear the allocated memory whether > > you're allocating from alloc_pages or from slab. What makes no sense > > is allocating an object from slab with a constructor *and* __GFP_ZERO. > > They're in conflict, and slab can't fulfill both of those requirements. > > It's a stable material. If you really think it does make sense, > please submit patch separately. > > > > > > > thread), but the right place to filter this out is in the caller of > > > > radix_tree_maybe_preload -- it's already filtering out HIGHMEM pages, > > > > and should filter out GFP_ZERO too. > > > > > > radix_tree_[maybe]_preload is exported API, which are error-prone > > > for out of modules or upcoming customers. > > > > > > More proper place is __radix_tree_preload. > > > > I could not disagree with you more. It is the responsibility of the > > callers of radix_tree_preload to avoid calling it with nonsense flags > > like __GFP_DMA, __GFP_HIGHMEM or __GFP_ZERO. > > How about this? > > It would fix current problem and warn potential bugs as well. > radix_tree_preload already has done such warning and > radix_tree_maybe_preload has skipping for misbehaivor gfp. > > From 27ecf7a009d3570d1155c528c7f08040ede68ed3 Mon Sep 17 00:00:00 2001 > From: Minchan Kim > Date: Tue, 10 Apr 2018 11:20:11 +0900 > Subject: [PATCH v2] mm: workingset: fix NULL ptr dereference > > It assumes shadow entries of radix tree rely on the init state > that node->private_list allocated newly is list_empty state > for the working. Currently, it's initailized in SLAB constructor > which means node of radix tree would be initialized only when > *slub allocates new page*, not *slub alloctes new object*. > > If some FS or subsystem pass gfp_mask to __GFP_ZERO, that means > newly allocated node can have !list_empty(node->private_list) > by memset of slab allocator. It ends up calling NULL deference > at workingset_update_node by failing list_empty check. > > This patch fixes it. > > Fixes: 449dd6984d0e ("mm: keep page cache radix tree nodes in check") > Cc: Johannes Weiner > Cc: Jan Kara > Cc: Matthew Wilcox > Cc: Jaegeuk Kim > Cc: Chao Yu > Cc: Christopher Lameter > Cc: linux-fsdevel@vger.kernel.org > Reported-by: Chris Fries > Signed-off-by: Minchan Kim > --- > lib/radix-tree.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/lib/radix-tree.c b/lib/radix-tree.c > index da9e10c827df..9d68f2a7888e 100644 > --- a/lib/radix-tree.c > +++ b/lib/radix-tree.c > @@ -511,6 +511,16 @@ int radix_tree_preload(gfp_t gfp_mask) > { > /* Warn on non-sensical use... */ > WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask)); > + /* > + * New allocate node must have node->private_list as INIT_LIST_HEAD > + * state by workingset shadow memory implementation. > + * If user pass __GFP_ZERO by mistake, slab allocator will clear > + * node->private_list, which makes a BUG. Rather than going Oops, > + * just fix and warn about it. > + */ > + if (WARN_ON(gfp_mask & __GFP_ZERO)) > + gfp_mask &= ~GFP_ZERO Build fail. If others are okay for this patch, I will resend fixed patch with stable mark. I will wait feedback from others. Thanks.