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=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 AA523C433B4 for ; Mon, 19 Apr 2021 08:49:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6664361107 for ; Mon, 19 Apr 2021 08:49:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238331AbhDSIuZ (ORCPT ); Mon, 19 Apr 2021 04:50:25 -0400 Received: from jabberwock.ucw.cz ([46.255.230.98]:37244 "EHLO jabberwock.ucw.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238385AbhDSIuZ (ORCPT ); Mon, 19 Apr 2021 04:50:25 -0400 Received: by jabberwock.ucw.cz (Postfix, from userid 1017) id 50B761C0B77; Mon, 19 Apr 2021 10:49:54 +0200 (CEST) Date: Mon, 19 Apr 2021 10:49:53 +0200 From: Pavel Machek To: Sasha Levin Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Aditya Pakki , Santosh Shilimkar , "David S . Miller" , netdev@vger.kernel.org, linux-rdma@vger.kernel.org, rds-devel@oss.oracle.com Subject: Re: [PATCH AUTOSEL 5.10 41/46] net/rds: Avoid potential use after free in rds_send_remove_from_sock Message-ID: <20210419084953.GA28564@amd> References: <20210412162401.314035-1-sashal@kernel.org> <20210412162401.314035-41-sashal@kernel.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="17pEHd4RhPHOinZp" Content-Disposition: inline In-Reply-To: <20210412162401.314035-41-sashal@kernel.org> User-Agent: Mutt/1.5.23 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org --17pEHd4RhPHOinZp Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi! > From: Aditya Pakki >=20 > [ Upstream commit 0c85a7e87465f2d4cbc768e245f4f45b2f299b05 ] >=20 > In case of rs failure in rds_send_remove_from_sock(), the 'rm' resource > is freed and later under spinlock, causing potential use-after-free. > Set the free pointer to NULL to avoid undefined behavior. This patch is crazy. It adds dead code. > +++ b/net/rds/message.c > @@ -180,6 +180,7 @@ void rds_message_put(struct rds_message *rm) > rds_message_purge(rm); > =20 > kfree(rm); > + rm =3D NULL; > } > } We are already exiting function, changing local variable has no effect. > +++ b/net/rds/send.c > @@ -665,7 +665,7 @@ static void rds_send_remove_from_sock(struct list_hea= d *messages, int status) > unlock_and_drop: > spin_unlock_irqrestore(&rm->m_rs_lock, flags); > rds_message_put(rm); > - if (was_on_sock) > + if (was_on_sock && rm) > rds_message_put(rm); > } If rm was non-NULL calling first rds_message_put (and it was, otherwise we oopsed), it is still non-NULL in second test. Best regards, Pavel --=20 'DENX Software Engineering GmbH, Managing Director: Wolfgang Denk' 'HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany' =09 --17pEHd4RhPHOinZp Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAmB9RDEACgkQMOfwapXb+vKCKACfbFn3RnqNFYdhDT2ym9rSlQMQ StcAoIdChJp23cIYf3KpweMUNitHrXv+ =4aJ2 -----END PGP SIGNATURE----- --17pEHd4RhPHOinZp--