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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 EA105C2D0EA for ; Thu, 9 Apr 2020 07:03:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C117A20757 for ; Thu, 9 Apr 2020 07:03:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586415781; bh=cWppHrDhyWFUnpfgT1RCt8t5EmUW09svhMX8f9UIxGI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=ujj+UGN6D/aJC8lCwLODeSKilQ9d1wVbIzDrOEV+ZeN49aT9dBe8Mzw7rhieBQvkp 22ZaKBI1UnsY4KqFXsEnCaBedG7NwtYTFg6KHSIdjXm7OLdKVMZhwIvvHEWFqGj367 yevSfRwf0hqDw69yidOfdWEkpmFEmdH7AtoO91Yw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726571AbgDIHDA (ORCPT ); Thu, 9 Apr 2020 03:03:00 -0400 Received: from mail-wr1-f67.google.com ([209.85.221.67]:39629 "EHLO mail-wr1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725783AbgDIHDA (ORCPT ); Thu, 9 Apr 2020 03:03:00 -0400 Received: by mail-wr1-f67.google.com with SMTP id p10so10603487wrt.6 for ; Thu, 09 Apr 2020 00:02:57 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=TOxDaT8KIKxTVyeGlG1DzjdQeiYJKvtYvDrAddTgvQ8=; b=fuQJvivam8DeVSIQ27XAr3uCcN6eBdmNJdJJY/H5NvzhqsRjIHbylMm3H7U4caIGCo RHe7evojXTHCLF6x6KlHH2vmrv7kTfA7a39Ils4bIfNdS9f8+7XZ6PvVsk+9rIyLp5B7 Tx+1cLIgd1biahLzMVzNvYfRQGUS495608zgmj1hbWMajvdVFC9Y4Dh/5NIwHIpopKrM Irvwk5EOTPHkPzIlU/CqFCy1SbbdGldhkPZdtwCLqKn1iYPkK3Qrbr258kCxLuqIOj+d u60OBwGV4yUsEHuZkIIFce+TcifsBhJBKvcQQ+jT1uTeHS30ZNAfe8v3JAH8V3V91qu/ 4Lvw== X-Gm-Message-State: AGi0PuZfn/QdbLS1q0w/SbGakFAl3mMEuVfAJZS6PohgwLkN1JzFrJWK gIR9AXm1mPfqZkqMefL+jOY= X-Google-Smtp-Source: APiQypIP8qkJwWE/4Q8GNBJ5qkqY5EM+Rw79dqUzcWC6hohz2gnvV0HVxwX8Lc5nsUDUozttdaXCHg== X-Received: by 2002:a5d:6a10:: with SMTP id m16mr13596846wru.371.1586415775488; Thu, 09 Apr 2020 00:02:55 -0700 (PDT) Received: from localhost (ip-37-188-180-223.eurotel.cz. [37.188.180.223]) by smtp.gmail.com with ESMTPSA id 91sm33867682wrf.79.2020.04.09.00.02.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Apr 2020 00:02:54 -0700 (PDT) Date: Thu, 9 Apr 2020 09:02:53 +0200 From: Michal Hocko To: Peter Xu Cc: linux-kernel@vger.kernel.org, Linus Torvalds , linux-mm@kvack.org, Andrew Morton , syzbot+693dc11fcb53120b5559@syzkaller.appspotmail.com Subject: Re: [PATCH 1/2] mm/mempolicy: Allow lookup_node() to handle fatal signal Message-ID: <20200409070253.GB18386@dhcp22.suse.cz> References: <20200408014010.80428-1-peterx@redhat.com> <20200408014010.80428-2-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200408014010.80428-2-peterx@redhat.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch has been merged and it is actually wrong after ae46d2aa6a7f has been merged. We can either revert or I suggest just handling >0, like the patch below: >From 03fbe30ec61e65b0927d0d41bccc7dff5f7eafd8 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Thu, 9 Apr 2020 08:26:57 +0200 Subject: [PATCH] mm, mempolicy: fix up gup usage in lookup_node ba841078cd05 ("mm/mempolicy: Allow lookup_node() to handle fatal signal") has added a special casing for 0 return value because that was a possible gup return value when interrupted by fatal signal. This has been fixed by ae46d2aa6a7f ("mm/gup: Let __get_user_pages_locked() return -EINTR for fatal signal") in the mean time so ba841078cd05 can be reverted. This patch however doesn't go all the way to revert it because 0 return value is impossible. We always get an error or 1 for a single page request. Fixes: ba841078cd05 ("mm/mempolicy: Allow lookup_node() to handle fatal signal") Signed-off-by: Michal Hocko --- mm/mempolicy.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 48ba9729062e..1965e2681877 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -927,10 +927,7 @@ static int lookup_node(struct mm_struct *mm, unsigned long addr) int locked = 1; err = get_user_pages_locked(addr & PAGE_MASK, 1, 0, &p, &locked); - if (err == 0) { - /* E.g. GUP interrupted by fatal signal */ - err = -EFAULT; - } else if (err > 0) { + if (err > 0) { err = page_to_nid(p); put_page(p); } -- 2.25.1 -- Michal Hocko SUSE Labs