From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e28smtp03.in.ibm.com (e28smtp03.in.ibm.com [122.248.162.3]) (using TLSv1 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 882D31A0B86 for ; Mon, 11 May 2015 16:28:40 +1000 (AEST) Received: from /spool/local by e28smtp03.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 11 May 2015 11:58:38 +0530 Received: from d28relay05.in.ibm.com (d28relay05.in.ibm.com [9.184.220.62]) by d28dlp01.in.ibm.com (Postfix) with ESMTP id E9C58E0056 for ; Mon, 11 May 2015 12:01:31 +0530 (IST) Received: from d28av01.in.ibm.com (d28av01.in.ibm.com [9.184.220.63]) by d28relay05.in.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t4B6SZx554853876 for ; Mon, 11 May 2015 11:58:35 +0530 Received: from d28av01.in.ibm.com (localhost [127.0.0.1]) by d28av01.in.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id t4B6SYhW013080 for ; Mon, 11 May 2015 11:58:35 +0530 From: "Aneesh Kumar K.V" To: benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au Subject: [PATCH V3] powerpc/mm: Return NULL for not present hugetlb page Date: Mon, 11 May 2015 11:58:29 +0530 Message-Id: <1431325709-21852-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Cc: linuxppc-dev@lists.ozlabs.org, "Aneesh Kumar K.V" List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , We need to check whether pte is present in follow_huge_addr and properly return NULL if mapping is not present. Also use READ_ONCE when dereferencing pte_t address. Without this patch, we may wrongly return a zero pfn page in follow_huge_addr. Reviewed-by: David Gibson Signed-off-by: Aneesh Kumar K.V --- Changes from V2: * Add Reviewed-by * Update commit message. arch/powerpc/mm/hugetlbpage.c | 25 ++++++++++++++++--------- 1 file changed, 16 insertions(+), 9 deletions(-) diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c index 0ce968b00b7c..3385e3d0506e 100644 --- a/arch/powerpc/mm/hugetlbpage.c +++ b/arch/powerpc/mm/hugetlbpage.c @@ -689,27 +689,34 @@ void hugetlb_free_pgd_range(struct mmu_gather *tlb, struct page * follow_huge_addr(struct mm_struct *mm, unsigned long address, int write) { - pte_t *ptep; - struct page *page; + pte_t *ptep, pte; unsigned shift; unsigned long mask, flags; + struct page *page = ERR_PTR(-EINVAL); + + local_irq_save(flags); + ptep = find_linux_pte_or_hugepte(mm->pgd, address, &shift); + if (!ptep) + goto no_page; + pte = READ_ONCE(*ptep); /* + * Verify it is a huge page else bail. * Transparent hugepages are handled by generic code. We can skip them * here. */ - local_irq_save(flags); - ptep = find_linux_pte_or_hugepte(mm->pgd, address, &shift); + if (!shift || pmd_trans_huge(__pmd(pte_val(pte)))) + goto no_page; - /* Verify it is a huge page else bail. */ - if (!ptep || !shift || pmd_trans_huge(*(pmd_t *)ptep)) { - local_irq_restore(flags); - return ERR_PTR(-EINVAL); + if (!pte_present(pte)) { + page = NULL; + goto no_page; } mask = (1UL << shift) - 1; - page = pte_page(*ptep); + page = pte_page(pte); if (page) page += (address & mask) / PAGE_SIZE; +no_page: local_irq_restore(flags); return page; } -- 2.1.4