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 X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2EE5FC433E7 for ; Mon, 19 Oct 2020 06:59:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C1A4622260 for ; Mon, 19 Oct 2020 06:59:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="cqeUAM00" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727208AbgJSG7Q (ORCPT ); Mon, 19 Oct 2020 02:59:16 -0400 Received: from mx2.suse.de ([195.135.220.15]:55750 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726985AbgJSG7Q (ORCPT ); Mon, 19 Oct 2020 02:59:16 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1603090754; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=WWTtNyRQpspwMkK1R2rGtDqE4M7Gn98Si984Ule9Ss0=; b=cqeUAM00YSlx6flc2JUsczFqRhNqcAHUth3ItSDuz5RcBKns5y+UKj2SW04npGOzplO9YM /DT91Bj0wyvPOyrLrw46mVjU+B12frH9ptun+N2UOsv+OH9mbOggNw76bVK0FqY9/zWm78 7bxFH5SZVDMwDg8OtCuas7X2YC2oOf8= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 3FE19ABD5; Mon, 19 Oct 2020 06:59:14 +0000 (UTC) Date: Mon, 19 Oct 2020 08:59:12 +0200 From: Michal Hocko To: Shijie Luo Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, osalvador@suse.de, linmiaohe@huawei.com, linfeilong@huawei.com Subject: Re: [PATCH V2] mm: fix potential pte_unmap_unlock pte error Message-ID: <20201019065912.GA27114@dhcp22.suse.cz> References: <20201017021151.28104-1-luoshijie1@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201017021151.28104-1-luoshijie1@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 16-10-20 22:11:51, Shijie Luo wrote: > When flags don't have MPOL_MF_MOVE or MPOL_MF_MOVE_ALL bits, code breaks > and passing origin pte - 1 to pte_unmap_unlock seems like not a good idea. This would really benefit from some improvements. It is preferable to provide a user visibile effect of the patch. I would propose this, feel free to reuse parts as you find fit. " queue_pages_pte_range can run in MPOL_MF_MOVE_ALL mode which doesn't migrate misplaced pages but returns with EIO when encountering such a page. Since a7f40cfe3b7a ("mm: mempolicy: make mbind() return -EIO when MPOL_MF_STRICT is specified") and early break on the first pte in the range results in pte_unmap_unlock on an underflow pte. This can lead to lockups later on when somebody tries to lock the pte resp. page_table_lock again.. Fixes: a7f40cfe3b7a ("mm: mempolicy: make mbind() return -EIO when MPOL_MF_STRICT is specified") " > Signed-off-by: Shijie Luo > Signed-off-by: Michal Hocko > Signed-off-by: Miaohe Lin No need to add my s-o-b. > --- > mm/mempolicy.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index 3fde772ef5ef..3ca4898f3f24 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -525,7 +525,7 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr, > unsigned long flags = qp->flags; > int ret; > bool has_unmovable = false; > - pte_t *pte; > + pte_t *pte, *mapped_pte; > spinlock_t *ptl; > > ptl = pmd_trans_huge_lock(pmd, vma); > @@ -539,7 +539,7 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr, > if (pmd_trans_unstable(pmd)) > return 0; > > - pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); > + mapped_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); > for (; addr != end; pte++, addr += PAGE_SIZE) { > if (!pte_present(*pte)) > continue; > @@ -571,7 +571,7 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr, > } else > break; > } > - pte_unmap_unlock(pte - 1, ptl); > + pte_unmap_unlock(mapped_pte, ptl); > cond_resched(); > > if (has_unmovable) > -- > 2.19.1 > -- Michal Hocko SUSE Labs