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=-13.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 B7EB5C433DB for ; Tue, 2 Mar 2021 17:40:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6A77564F04 for ; Tue, 2 Mar 2021 17:40:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349802AbhCBRgn convert rfc822-to-8bit (ORCPT ); Tue, 2 Mar 2021 12:36:43 -0500 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.85.151]:26380 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1384474AbhCBPFV (ORCPT ); Tue, 2 Mar 2021 10:05:21 -0500 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-55-u2cLqoF3NgiPbPzefNzsww-1; Tue, 02 Mar 2021 14:59:19 +0000 X-MC-Unique: u2cLqoF3NgiPbPzefNzsww-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Tue, 2 Mar 2021 14:59:17 +0000 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Tue, 2 Mar 2021 14:59:17 +0000 From: David Laight To: 'Wang Qing' , Andrew Morton , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH] mm: Return -EFAULT if copy_to_user() fails Thread-Topic: [PATCH] mm: Return -EFAULT if copy_to_user() fails Thread-Index: AQHXDpc1nTDef+ZvgkK8MJDT0a5yVapwy5xQ Date: Tue, 2 Mar 2021 14:59:17 +0000 Message-ID: References: <1614601963-25812-1-git-send-email-wangqing@vivo.com> In-Reply-To: <1614601963-25812-1-git-send-email-wangqing@vivo.com> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Wang Qing > Sent: 01 March 2021 12:33 > > The copy_to_user() function returns the number of bytes remaining to be > copied, but we want to return -EFAULT if the copy doesn't complete. > > Signed-off-by: Wang Qing > --- > mm/mempolicy.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index ab51132..a116e56 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -1667,7 +1667,7 @@ COMPAT_SYSCALL_DEFINE5(get_mempolicy, int __user *, policy, > if (!err && nmask) { > unsigned long copy_size; > copy_size = min_t(unsigned long, sizeof(bm), alloc_size); > - err = copy_from_user(bm, nm, copy_size); > + err = copy_from_user(bm, nm, copy_size) ? -EFAULT : 0; > /* ensure entire bitmap is zeroed */ > err |= clear_user(nmask, ALIGN(maxnode-1, 8) / 8); > err |= compat_put_bitmap(nmask, bm, nr_bits); Given the 'err |= xxx' that follow I suspect the error code doesn't matter at all. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)