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Wed, 11 Apr 2018 02:03:29 -0400 From: Matthew Wilcox To: linux-mm@kvack.org Cc: Matthew Wilcox , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , linux-kernel@vger.kernel.org, Jan Kara , Jeff Layton , Mel Gorman , stable@vger.kernel.org Subject: [PATCH v2 1/2] Fix NULL pointer in page_cache_tree_insert Date: Tue, 10 Apr 2018 23:03:19 -0700 Message-Id: <20180411060320.14458-2-willy@infradead.org> X-Mailer: git-send-email 2.14.3 In-Reply-To: <20180411060320.14458-1-willy@infradead.org> References: <20180411060320.14458-1-willy@infradead.org> Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: From: Matthew Wilcox f2fs specifies the __GFP_ZERO flag for allocating some of its pages. Unfortunately, the page cache also uses the mapping's GFP flags for allocating radix tree nodes. It always masked off the __GFP_HIGHMEM flag, and masks off __GFP_ZERO in some paths, but not all. That causes radix tree nodes to be allocated with a NULL list_head, which causes backtraces like: [] __list_del_entry+0x30/0xd0 [] list_lru_del+0xac/0x1ac [] page_cache_tree_insert+0xd8/0x110 The __GFP_DMA and __GFP_DMA32 flags would also be able to sneak through if they are ever used. Fix them all by using GFP_RECLAIM_MASK at the innermost location, and remove it from earlier in the callchain. Fixes: 449dd6984d0e ("mm: keep page cache radix tree nodes in check") Reported-by: Chris Fries Debugged-by: Minchan Kim Signed-off-by: Matthew Wilcox Acked-by: Johannes Weiner Acked-by: Michal Hocko Reviewed-by: Jan Kara Cc: stable@vger.kernel.org --- mm/filemap.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index c2147682f4c3..1a4bfc5ed3dc 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -785,7 +785,7 @@ 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_RECLAIM_MASK); if (!error) { struct address_space *mapping = old->mapping; void (*freepage)(struct page *); @@ -841,7 +841,7 @@ 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_RECLAIM_MASK); if (error) { if (!huge) mem_cgroup_cancel_charge(page, memcg, false); @@ -1574,8 +1574,7 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset, if (fgp_flags & FGP_ACCESSED) __SetPageReferenced(page); - err = add_to_page_cache_lru(page, mapping, offset, - gfp_mask & GFP_RECLAIM_MASK); + err = add_to_page_cache_lru(page, mapping, offset, gfp_mask); if (unlikely(err)) { put_page(page); page = NULL; @@ -2378,7 +2377,7 @@ static int page_cache_read(struct file *file, pgoff_t offset, gfp_t gfp_mask) if (!page) return -ENOMEM; - ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask & GFP_KERNEL); + ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask); if (ret == 0) ret = mapping->a_ops->readpage(file, page); else if (ret == -EEXIST) -- 2.16.3