From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.85.151]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4418A3FD3 for ; Thu, 2 Sep 2021 14:03:21 +0000 (UTC) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-90-tzR3TaFjMtSaC8iSrW3zwg-1; Thu, 02 Sep 2021 15:03:18 +0100 X-MC-Unique: tzR3TaFjMtSaC8iSrW3zwg-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.23; Thu, 2 Sep 2021 15:03:17 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.023; Thu, 2 Sep 2021 15:03:17 +0100 From: David Laight To: 'Joe Perches' , Kari Argillander , Konstantin Komarov , "ntfs3@lists.linux.dev" CC: "linux-kernel@vger.kernel.org" Subject: RE: [PATCH 1/5] fs/ntfs3: Use kmalloc_array over kmalloc with multiply Thread-Topic: [PATCH 1/5] fs/ntfs3: Use kmalloc_array over kmalloc with multiply Thread-Index: AQHXntrPdHiUovXUwEmoBRmrkk5W9KuQyAlw Date: Thu, 2 Sep 2021 14:03:17 +0000 Message-ID: <6c078835254b43ec82bf45db3b241510@AcuMS.aculab.com> References: <20210831181505.1074767-1-kari.argillander@gmail.com> <20210831181505.1074767-2-kari.argillander@gmail.com> <5197939870d1867dd2131a8fdff8842b777c6016.camel@perches.com> In-Reply-To: <5197939870d1867dd2131a8fdff8842b777c6016.camel@perches.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] Precedence: bulk X-Mailing-List: ntfs3@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: 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: quoted-printable From: Joe Perches > Sent: 01 September 2021 03:41 >=20 > On Tue, 2021-08-31 at 21:15 +0300, Kari Argillander wrote: > > If we do not use kmalloc_array we get checkpatch warning. It is also > > little safer if something goes wrong with coding. > [] > > diff --git a/fs/ntfs3/index.c b/fs/ntfs3/index.c > [] > > @@ -707,7 +707,7 @@ static struct NTFS_DE *hdr_find_e(const struct ntfs= _index *indx, > > =C2=A0=09=09u16 *ptr; > > =C2=A0=09=09int new_slots =3D ALIGN(2 * nslots, 8); > > > > > > -=09=09ptr =3D kmalloc(sizeof(u16) * new_slots, GFP_NOFS); > > +=09=09ptr =3D kmalloc_array(new_slots, sizeof(u16), GFP_NOFS); > > =C2=A0=09=09if (ptr) > > =C2=A0=09=09=09memcpy(ptr, offs, sizeof(u16) * max_idx); >=20 > This multiplication could also overflow. Not if kmalloc_array() has suceeded. OTOH the ALIGN(2 * nslots, 8) can also go wrong. (But probably not if the previous kmalloc() for 1/2 the size worked.) But there really ought to be some kind of bound check earlier. =09David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1= PT, UK Registration No: 1397386 (Wales)