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[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> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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