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Mon, 09 Apr 2018 19:59:08 -0700 (PDT) Date: Tue, 10 Apr 2018 11:59:03 +0900 From: Minchan Kim 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 Subject: Re: [PATCH] mm: workingset: fix NULL ptr dereference Message-ID: <20180410025903.GA38000@rodete-desktop-imager.corp.google.com> References: <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> <20180410024152.GC31282@bombadil.infradead.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20180410024152.GC31282@bombadil.infradead.org> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Mon, Apr 09, 2018 at 07:41:52PM -0700, Matthew Wilcox wrote: > On Tue, Apr 10, 2018 at 11:33:39AM +0900, Minchan Kim wrote: > > @@ -522,7 +532,7 @@ EXPORT_SYMBOL(radix_tree_preload); > > */ > > int radix_tree_maybe_preload(gfp_t gfp_mask) > > { > > - if (gfpflags_allow_blocking(gfp_mask)) > > + if (gfpflags_allow_blocking(gfp_mask) && !(gfp_mask & __GFP_ZERO)) > > return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE); > > /* Preloading doesn't help anything with this gfp mask, skip it */ > > preempt_disable(); > > No, you've completely misunderstood what's going on in this function. Okay, I hope this version clear current concerns. From fb37c41b90f7d3ead1798e5cb7baef76709afd94 Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Tue, 10 Apr 2018 11:54:57 +0900 Subject: [PATCH v3] 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 Cc: stable@vger.kernel.org Reported-by: Chris Fries Signed-off-by: Minchan Kim Reviewed-by: Jan Kara --- lib/radix-tree.c | 9 +++++++++ mm/filemap.c | 5 +++-- 2 files changed, 12 insertions(+), 2 deletions(-) diff --git a/lib/radix-tree.c b/lib/radix-tree.c index da9e10c827df..7569e637dbaa 100644 --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -470,6 +470,15 @@ static __must_check int __radix_tree_preload(gfp_t gfp_mask, unsigned nr) struct radix_tree_node *node; int ret = -ENOMEM; + /* + * 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; /* * Nodes preloaded by one cgroup can be be used by another cgroup, so * they should never be accounted to any particular memory cgroup. diff --git a/mm/filemap.c b/mm/filemap.c index ab77e19ab09c..b6de9d691c8a 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -786,7 +786,7 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask) VM_BUG_ON_PAGE(!PageLocked(new), new); VM_BUG_ON_PAGE(new->mapping, new); - error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM); + error = radix_tree_preload(gfp_mask & ~(__GFP_HIGHMEM | __GFP_ZERO)); if (!error) { struct address_space *mapping = old->mapping; void (*freepage)(struct page *); @@ -842,7 +842,8 @@ static int __add_to_page_cache_locked(struct page *page, return error; } - error = radix_tree_maybe_preload(gfp_mask & ~__GFP_HIGHMEM); + error = radix_tree_maybe_preload(gfp_mask & + ~(__GFP_HIGHMEM | __GFP_ZERO)); if (error) { if (!huge) mem_cgroup_cancel_charge(page, memcg, false);