linux-kernel - Re: [PATCH 1/2] mm/mempolicy: Allow lookup

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20200409070253.GB18386@dhcp22.suse.cz>
Date:   Thu, 9 Apr 2020 09:02:53 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Peter Xu <peterx@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        syzbot+693dc11fcb53120b5559@...kaller.appspotmail.com
Subject: Re: [PATCH 1/2] mm/mempolicy: Allow lookup_node() to handle fatal
 signal

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 <mhocko@...e.com>
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 <mhocko@...e.com>
---
 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