From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ua0-f199.google.com (mail-ua0-f199.google.com [209.85.217.199]) by kanga.kvack.org (Postfix) with ESMTP id F272E6B0292 for ; Tue, 18 Jul 2017 15:40:13 -0400 (EDT) Received: by mail-ua0-f199.google.com with SMTP id h2so21550203uaf.5 for ; Tue, 18 Jul 2017 12:40:13 -0700 (PDT) Received: from aserp1040.oracle.com (aserp1040.oracle.com. [141.146.126.69]) by mx.google.com with ESMTPS id 4si1210138vko.190.2017.07.18.12.40.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 Jul 2017 12:40:13 -0700 (PDT) From: daniel.m.jordan@oracle.com Subject: [PATCH] mm/hugetlb: __get_user_pages ignores certain follow_hugetlb_page errors Date: Tue, 18 Jul 2017 12:39:55 -0700 Message-Id: <1500406795-58462-1-git-send-email-daniel.m.jordan@oracle.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: aarcange@redhat.com, akpm@linux-foundation.org, aneesh.kumar@linux.vnet.ibm.com, gerald.schaefer@de.ibm.com, james.morse@arm.com, kirill.shutemov@linux.intel.com, mhocko@suse.com, mike.kravetz@oracle.com, n-horiguchi@ah.jp.nec.com, punit.agrawal@arm.com, zhongjiang@huawei.com, linux-kernel@vger.kernel.org Commit 9a291a7c9428 ("mm/hugetlb: report -EHWPOISON not -EFAULT when FOLL_HWPOISON is specified") causes __get_user_pages to ignore certain errors from follow_hugetlb_page. After such error, __get_user_pages subsequently calls faultin_page on the same VMA and start address that follow_hugetlb_page failed on instead of returning the error immediately as it should. In follow_hugetlb_page, when hugetlb_fault returns a value covered under VM_FAULT_ERROR, follow_hugetlb_page returns it without setting nr_pages to 0 as __get_user_pages expects in this case, which causes the following to happen in __get_user_pages: the "while (nr_pages)" check succeeds, we skip the "if (!vma..." check because we got a VMA the last time around, we find no page with follow_page_mask, and we call faultin_page, which calls hugetlb_fault for the second time. This issue also slightly changes how __get_user_pages works. Before, it only returned error if it had made no progress (i = 0). But now, follow_hugetlb_page can clobber "i" with an error code since its new return path doesn't check for progress. So if "i" is nonzero before a failing call to follow_hugetlb_page, that indication of progress is lost and __get_user_pages can return error even if some pages were successfully pinned. To fix this, change follow_hugetlb_page so that it updates nr_pages, allowing __get_user_pages to fail immediately and restoring the "error only if no progress" behavior to __get_user_pages. Tested that __get_user_pages returns when expected on error from hugetlb_fault in follow_hugetlb_page. Fixes: 9a291a7c9428 ("mm/hugetlb: report -EHWPOISON not -EFAULT when FOLL_HWPOISON is specified") Signed-off-by: Daniel Jordan Cc: Andrea Arcangeli Cc: Andrew Morton Cc: "Aneesh Kumar K.V" Cc: Gerald Schaefer Cc: James Morse Cc: "Kirill A. Shutemov" Cc: Michal Hocko Cc: Mike Kravetz Cc: Naoya Horiguchi Cc: Punit Agrawal Cc: zhong jiang --- mm/hugetlb.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 3eedb18..cc28993 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4095,6 +4095,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long vaddr = *position; unsigned long remainder = *nr_pages; struct hstate *h = hstate_vma(vma); + int err = -EFAULT; while (vaddr < vma->vm_end && remainder) { pte_t *pte; @@ -4170,11 +4171,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, } ret = hugetlb_fault(mm, vma, vaddr, fault_flags); if (ret & VM_FAULT_ERROR) { - int err = vm_fault_to_errno(ret, flags); - - if (err) - return err; - + err = vm_fault_to_errno(ret, flags); remainder = 0; break; } @@ -4229,7 +4226,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, */ *position = vaddr; - return i ? i : -EFAULT; + return i ? i : err; } #ifndef __HAVE_ARCH_FLUSH_HUGETLB_TLB_RANGE -- 1.8.3.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org