From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 15EFFC433EF for ; Mon, 1 Nov 2021 09:45:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F008060F24 for ; Mon, 1 Nov 2021 09:45:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234247AbhKAJry (ORCPT ); Mon, 1 Nov 2021 05:47:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:47954 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234070AbhKAJoD (ORCPT ); Mon, 1 Nov 2021 05:44:03 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 935AD613AC; Mon, 1 Nov 2021 09:29:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1635758952; bh=GA2hlOhbGhLagM91qDwlQuRU7FkajjPv2qPzrSTmosA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=S1piglzXoGBiauoh0rDUfk8mZgmgSGbfva7YIC6HaDo1jocY/ZYPiuzUoecJFVowM nXIbl9rj/zUeGf5amsBhsL7kxm9rjbWUaPsd5GuEZtR5JHI0HQzWYapKyeX4HXFRX4 8RMAXbeTt8hnuwVsS0v+b2DXPYppZQ+LdB9/cAgE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Yang Shi , Naoya Horiguchi , "Kirill A. Shutemov" , Hugh Dickins , Matthew Wilcox , Oscar Salvador , Peter Xu , Andrew Morton , Linus Torvalds Subject: [PATCH 5.14 034/125] mm: filemap: check if THP has hwpoisoned subpage for PMD page fault Date: Mon, 1 Nov 2021 10:16:47 +0100 Message-Id: <20211101082539.647144926@linuxfoundation.org> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211101082533.618411490@linuxfoundation.org> References: <20211101082533.618411490@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yang Shi commit eac96c3efdb593df1a57bb5b95dbe037bfa9a522 upstream. When handling shmem page fault the THP with corrupted subpage could be PMD mapped if certain conditions are satisfied. But kernel is supposed to send SIGBUS when trying to map hwpoisoned page. There are two paths which may do PMD map: fault around and regular fault. Before commit f9ce0be71d1f ("mm: Cleanup faultaround and finish_fault() codepaths") the thing was even worse in fault around path. The THP could be PMD mapped as long as the VMA fits regardless what subpage is accessed and corrupted. After this commit as long as head page is not corrupted the THP could be PMD mapped. In the regular fault path the THP could be PMD mapped as long as the corrupted page is not accessed and the VMA fits. This loophole could be fixed by iterating every subpage to check if any of them is hwpoisoned or not, but it is somewhat costly in page fault path. So introduce a new page flag called HasHWPoisoned on the first tail page. It indicates the THP has hwpoisoned subpage(s). It is set if any subpage of THP is found hwpoisoned by memory failure and after the refcount is bumped successfully, then cleared when the THP is freed or split. The soft offline path doesn't need this since soft offline handler just marks a subpage hwpoisoned when the subpage is migrated successfully. But shmem THP didn't get split then migrated at all. Link: https://lkml.kernel.org/r/20211020210755.23964-3-shy828301@gmail.com Fixes: 800d8c63b2e9 ("shmem: add huge pages support") Signed-off-by: Yang Shi Reviewed-by: Naoya Horiguchi Suggested-by: Kirill A. Shutemov Cc: Hugh Dickins Cc: Matthew Wilcox Cc: Oscar Salvador Cc: Peter Xu Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- include/linux/page-flags.h | 23 +++++++++++++++++++++++ mm/huge_memory.c | 2 ++ mm/memory-failure.c | 14 ++++++++++++++ mm/memory.c | 9 +++++++++ mm/page_alloc.c | 4 +++- 5 files changed, 51 insertions(+), 1 deletion(-) --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -171,6 +171,15 @@ enum pageflags { /* Compound pages. Stored in first tail page's flags */ PG_double_map = PG_workingset, +#ifdef CONFIG_MEMORY_FAILURE + /* + * Compound pages. Stored in first tail page's flags. + * Indicates that at least one subpage is hwpoisoned in the + * THP. + */ + PG_has_hwpoisoned = PG_mappedtodisk, +#endif + /* non-lru isolated movable page */ PG_isolated = PG_reclaim, @@ -703,6 +712,20 @@ PAGEFLAG_FALSE(DoubleMap) TESTSCFLAG_FALSE(DoubleMap) #endif +#if defined(CONFIG_MEMORY_FAILURE) && defined(CONFIG_TRANSPARENT_HUGEPAGE) +/* + * PageHasHWPoisoned indicates that at least one subpage is hwpoisoned in the + * compound page. + * + * This flag is set by hwpoison handler. Cleared by THP split or free page. + */ +PAGEFLAG(HasHWPoisoned, has_hwpoisoned, PF_SECOND) + TESTSCFLAG(HasHWPoisoned, has_hwpoisoned, PF_SECOND) +#else +PAGEFLAG_FALSE(HasHWPoisoned) + TESTSCFLAG_FALSE(HasHWPoisoned) +#endif + /* * Check if a page is currently marked HWPoisoned. Note that this check is * best effort only and inherently racy: there is no way to synchronize with --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2452,6 +2452,8 @@ static void __split_huge_page(struct pag /* lock lru list/PageCompound, ref frozen by page_ref_freeze */ lruvec = lock_page_lruvec(head); + ClearPageHasHWPoisoned(head); + for (i = nr - 1; i >= 1; i--) { __split_huge_page_tail(head, i, lruvec, list); /* Some pages can be beyond i_size: drop them from page cache */ --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1694,6 +1694,20 @@ try_again: } if (PageTransHuge(hpage)) { + /* + * The flag must be set after the refcount is bumped + * otherwise it may race with THP split. + * And the flag can't be set in get_hwpoison_page() since + * it is called by soft offline too and it is just called + * for !MF_COUNT_INCREASE. So here seems to be the best + * place. + * + * Don't need care about the above error handling paths for + * get_hwpoison_page() since they handle either free page + * or unhandlable page. The refcount is bumped iff the + * page is a valid handlable page. + */ + SetPageHasHWPoisoned(hpage); if (try_to_split_thp_page(p, "Memory Failure") < 0) { action_result(pfn, MF_MSG_UNSPLIT_THP, MF_IGNORED); res = -EBUSY; --- a/mm/memory.c +++ b/mm/memory.c @@ -3906,6 +3906,15 @@ vm_fault_t do_set_pmd(struct vm_fault *v return ret; /* + * Just backoff if any subpage of a THP is corrupted otherwise + * the corrupted page may mapped by PMD silently to escape the + * check. This kind of THP just can be PTE mapped. Access to + * the corrupted subpage should trigger SIGBUS as expected. + */ + if (unlikely(PageHasHWPoisoned(page))) + return ret; + + /* * Archs like ppc64 need additional space to store information * related to pte entry. Use the preallocated table for that. */ --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1320,8 +1320,10 @@ static __always_inline bool free_pages_p VM_BUG_ON_PAGE(compound && compound_order(page) != order, page); - if (compound) + if (compound) { ClearPageDoubleMap(page); + ClearPageHasHWPoisoned(page); + } for (i = 1; i < (1 << order); i++) { if (compound) bad += free_tail_pages_check(page, page + i);