From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f174.google.com (mail-pd0-f174.google.com [209.85.192.174]) by kanga.kvack.org (Postfix) with ESMTP id 8ECA16B0074 for ; Thu, 19 Mar 2015 13:08:47 -0400 (EDT) Received: by pdnc3 with SMTP id c3so81802958pdn.0 for ; Thu, 19 Mar 2015 10:08:47 -0700 (PDT) Received: from mga09.intel.com (mga09.intel.com. [134.134.136.24]) by mx.google.com with ESMTP id fe5si4251976pdb.39.2015.03.19.10.08.42 for ; Thu, 19 Mar 2015 10:08:42 -0700 (PDT) From: "Kirill A. Shutemov" Subject: [PATCH 16/16] mm: sanitize page->mapping for tail pages Date: Thu, 19 Mar 2015 19:08:22 +0200 Message-Id: <1426784902-125149-17-git-send-email-kirill.shutemov@linux.intel.com> In-Reply-To: <1426784902-125149-1-git-send-email-kirill.shutemov@linux.intel.com> References: <1426784902-125149-1-git-send-email-kirill.shutemov@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , Andrea Arcangeli , Hugh Dickins Cc: Dave Hansen , Mel Gorman , Rik van Riel , Vlastimil Babka , Christoph Lameter , Naoya Horiguchi , Steve Capper , "Aneesh Kumar K.V" , Johannes Weiner , Michal Hocko , Jerome Marchand , linux-kernel@vger.kernel.org, linux-mm@kvack.org, "Kirill A. Shutemov" We don't define meaning of page->mapping for tail pages. Currently it's always NULL, which can be inconsistent with head page and potentially lead to problems. Let's poison the pointer to catch all illigal uses. page_rmapping() and page_mapping() are changed to look on head page. The only illigal use I've catched so far is __GPF_COMP pages from sound subsystem, mapped with PTEs. do_shared_fault() is changed to use page_rmapping() instead of direct access to fault_page->mapping. Signed-off-by: Kirill A. Shutemov --- include/linux/mm.h | 1 + include/linux/poison.h | 4 ++++ mm/huge_memory.c | 2 +- mm/memory.c | 2 +- mm/page_alloc.c | 7 +++++++ mm/util.c | 5 ++++- 6 files changed, 18 insertions(+), 3 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index bcf37dacbee3..4a3a38522ab4 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -915,6 +915,7 @@ extern struct address_space *page_mapping(struct page *page); /* Neutral page->mapping pointer to address_space or anon_vma or other */ static inline void *page_rmapping(struct page *page) { + page = compound_head(page); return (void *)((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS); } diff --git a/include/linux/poison.h b/include/linux/poison.h index 2110a81c5e2a..7b2a7fcde6a3 100644 --- a/include/linux/poison.h +++ b/include/linux/poison.h @@ -32,6 +32,10 @@ /********** mm/debug-pagealloc.c **********/ #define PAGE_POISON 0xaa +/********** mm/page_alloc.c ************/ + +#define TAIL_MAPPING ((void *) 0x01014A11 + POISON_POINTER_DELTA) + /********** mm/slab.c **********/ /* * Magic nums for obj red zoning. diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 3412cc8a4bd4..54d90ed2d31b 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1739,7 +1739,7 @@ static void __split_huge_page_refcount(struct page *page, */ page_tail->_mapcount = page->_mapcount; - BUG_ON(page_tail->mapping); + BUG_ON(page_tail->mapping != TAIL_MAPPING); page_tail->mapping = page->mapping; page_tail->index = page->index + i; diff --git a/mm/memory.c b/mm/memory.c index 5ec794f13f8a..a76f61aa88da 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3033,7 +3033,7 @@ static int do_shared_fault(struct mm_struct *mm, struct vm_area_struct *vma, * pinned by vma->vm_file's reference. We rely on unlock_page()'s * release semantics to prevent the compiler from undoing this copying. */ - mapping = fault_page->mapping; + mapping = page_rmapping(fault_page); unlock_page(fault_page); if ((dirtied || vma->vm_ops->page_mkwrite) && mapping) { /* diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 1b849500640c..e73ecbbfa69f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -373,6 +373,7 @@ void prep_compound_page(struct page *page, unsigned long order) for (i = 1; i < nr_pages; i++) { struct page *p = page + i; set_page_count(p, 0); + p->mapping = TAIL_MAPPING; p->first_page = page; /* Make sure p->first_page is always valid for PageTail() */ smp_wmb(); @@ -765,6 +766,12 @@ static void free_one_page(struct zone *zone, static int free_tail_pages_check(struct page *head_page, struct page *page) { + if (page->mapping != TAIL_MAPPING) { + bad_page(page, "corrupted mapping in tail page", 0); + page->mapping = NULL; + return 1; + } + page->mapping = NULL; if (!IS_ENABLED(CONFIG_DEBUG_VM)) return 0; if (unlikely(!PageTail(page))) { diff --git a/mm/util.c b/mm/util.c index d68339206100..769a7a2870af 100644 --- a/mm/util.c +++ b/mm/util.c @@ -357,7 +357,10 @@ EXPORT_SYMBOL(kvfree); struct address_space *page_mapping(struct page *page) { - struct address_space *mapping = page->mapping; + struct address_space *mapping; + + page = compound_head(page); + mapping = page->mapping; /* This happens if someone calls flush_dcache_page on slab page */ if (unlikely(PageSlab(page))) -- 2.1.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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