From patchwork Mon Feb 22 15:12:46 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Oleksij Rempel X-Patchwork-Id: 386545 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=-16.7 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, USER_AGENT_GIT autolearn=unavailable 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 4753AC433DB for ; Mon, 22 Feb 2021 15:17:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ECF8264E77 for ; Mon, 22 Feb 2021 15:17:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230309AbhBVPQy (ORCPT ); Mon, 22 Feb 2021 10:16:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40118 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231363AbhBVPPM (ORCPT ); Mon, 22 Feb 2021 10:15:12 -0500 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C3089C061A2B for ; Mon, 22 Feb 2021 07:13:01 -0800 (PST) Received: from dude.hi.pengutronix.de ([2001:67c:670:100:1d::7]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1lECtF-0007dt-CX; Mon, 22 Feb 2021 16:12:49 +0100 Received: from ore by dude.hi.pengutronix.de with local (Exim 4.92) (envelope-from ) id 1lECtE-00073i-EI; Mon, 22 Feb 2021 16:12:48 +0100 From: Oleksij Rempel To: mkl@pengutronix.de, "David S. Miller" , Jakub Kicinski , Oliver Hartkopp , Robin van der Gracht , Johannes Berg Cc: Oleksij Rempel , Andre Naujoks , Eric Dumazet , kernel@pengutronix.de, linux-can@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org Subject: [PATCH net v1 2/3] can: fix ref count warning if socket was closed before skb was cloned Date: Mon, 22 Feb 2021 16:12:46 +0100 Message-Id: <20210222151247.24534-3-o.rempel@pengutronix.de> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210222151247.24534-1-o.rempel@pengutronix.de> References: <20210222151247.24534-1-o.rempel@pengutronix.de> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::7 X-SA-Exim-Mail-From: ore@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-wireless@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org There are two ref count variables controlling the free()ing of a socket: - struct sock::sk_refcnt - which is changed by sock_hold()/sock_put() - struct sock::sk_wmem_alloc - which accounts the memory allocated by the skbs in the send path. If the socket is closed the struct sock::sk_refcnt will finally reach 0 and sk_free() is called. Which then calls refcount_dec_and_test(&sk->sk_wmem_alloc). If sk_wmem_alloc reaches 0 the socket is actually free()ed. In case there are still TX skbs on the fly and the socket() is closed, the struct sock::sk_refcnt reaches 0. In the TX-path the CAN stack clones an "echo" skb, calls sock_hold() on the original socket and references it. This produces the following back trace: | WARNING: CPU: 0 PID: 280 at lib/refcount.c:25 refcount_warn_saturate+0x114/0x134 | refcount_t: addition on 0; use-after-free. | Modules linked in: coda_vpu(E) v4l2_jpeg(E) videobuf2_vmalloc(E) imx_vdoa(E) | CPU: 0 PID: 280 Comm: test_can.sh Tainted: G E 5.11.0-04577-gf8ff6603c617 #203 | Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree) | Backtrace: | [<80bafea4>] (dump_backtrace) from [<80bb0280>] (show_stack+0x20/0x24) r7:00000000 r6:600f0113 r5:00000000 r4:81441220 | [<80bb0260>] (show_stack) from [<80bb593c>] (dump_stack+0xa0/0xc8) | [<80bb589c>] (dump_stack) from [<8012b268>] (__warn+0xd4/0x114) r9:00000019 r8:80f4a8c2 r7:83e4150c r6:00000000 r5:00000009 r4:80528f90 | [<8012b194>] (__warn) from [<80bb09c4>] (warn_slowpath_fmt+0x88/0xc8) r9:83f26400 r8:80f4a8d1 r7:00000009 r6:80528f90 r5:00000019 r4:80f4a8c2 | [<80bb0940>] (warn_slowpath_fmt) from [<80528f90>] (refcount_warn_saturate+0x114/0x134) r8:00000000 r7:00000000 r6:82b44000 r5:834e5600 r4:83f4d540 | [<80528e7c>] (refcount_warn_saturate) from [<8079a4c8>] (__refcount_add.constprop.0+0x4c/0x50) | [<8079a47c>] (__refcount_add.constprop.0) from [<8079a57c>] (can_put_echo_skb+0xb0/0x13c) | [<8079a4cc>] (can_put_echo_skb) from [<8079ba98>] (flexcan_start_xmit+0x1c4/0x230) r9:00000010 r8:83f48610 r7:0fdc0000 r6:0c080000 r5:82b44000 r4:834e5600 | [<8079b8d4>] (flexcan_start_xmit) from [<80969078>] (netdev_start_xmit+0x44/0x70) r9:814c0ba0 r8:80c8790c r7:00000000 r6:834e5600 r5:82b44000 r4:82ab1f00 | [<80969034>] (netdev_start_xmit) from [<809725a4>] (dev_hard_start_xmit+0x19c/0x318) r9:814c0ba0 r8:00000000 r7:82ab1f00 r6:82b44000 r5:00000000 r4:834e5600 | [<80972408>] (dev_hard_start_xmit) from [<809c6584>] (sch_direct_xmit+0xcc/0x264) r10:834e5600 r9:00000000 r8:00000000 r7:82b44000 r6:82ab1f00 r5:834e5600 r4:83f27400 | [<809c64b8>] (sch_direct_xmit) from [<809c6c0c>] (__qdisc_run+0x4f0/0x534) To fix this problem, we have to take into account, that the socket technically still there but should not used (by any new skbs) any more. The function skb_clone_sk_optional() (introduced in the previous patch) takes care of this. It will only clone the skb, if the sk is set and the refcount has not reached 0. Cc: Oliver Hartkopp Cc: Andre Naujoks Cc: Eric Dumazet Fixes: 0ae89beb283a ("can: add destructor for self generated skbs") Signed-off-by: Oleksij Rempel --- include/linux/can/skb.h | 3 +-- net/can/af_can.c | 6 +++--- net/can/j1939/main.c | 3 +-- net/can/j1939/socket.c | 3 +-- net/can/j1939/transport.c | 4 +--- 5 files changed, 7 insertions(+), 12 deletions(-) diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h index 685f34cfba20..bc1af38697a2 100644 --- a/include/linux/can/skb.h +++ b/include/linux/can/skb.h @@ -79,13 +79,12 @@ static inline struct sk_buff *can_create_echo_skb(struct sk_buff *skb) { struct sk_buff *nskb; - nskb = skb_clone(skb, GFP_ATOMIC); + nskb = skb_clone_sk_optional(skb); if (unlikely(!nskb)) { kfree_skb(skb); return NULL; } - can_skb_set_owner(nskb, skb->sk); consume_skb(skb); return nskb; } diff --git a/net/can/af_can.c b/net/can/af_can.c index cce2af10eb3e..9e1bd60e7e1b 100644 --- a/net/can/af_can.c +++ b/net/can/af_can.c @@ -251,20 +251,20 @@ int can_send(struct sk_buff *skb, int loop) * its own. Example: can_raw sockopt CAN_RAW_RECV_OWN_MSGS * Therefore we have to ensure that skb->sk remains the * reference to the originating sock by restoring skb->sk - * after each skb_clone() or skb_orphan() usage. + * after each skb_clone() or skb_orphan() usage - + * skb_clone_sk_optional() takes care of that. */ if (!(skb->dev->flags & IFF_ECHO)) { /* If the interface is not capable to do loopback * itself, we do it here. */ - newskb = skb_clone(skb, GFP_ATOMIC); + newskb = skb_clone_sk_optional(skb); if (!newskb) { kfree_skb(skb); return -ENOMEM; } - can_skb_set_owner(newskb, skb->sk); newskb->ip_summed = CHECKSUM_UNNECESSARY; newskb->pkt_type = PACKET_BROADCAST; } diff --git a/net/can/j1939/main.c b/net/can/j1939/main.c index da3a7a7bcff2..4f6852d48077 100644 --- a/net/can/j1939/main.c +++ b/net/can/j1939/main.c @@ -47,12 +47,11 @@ static void j1939_can_recv(struct sk_buff *iskb, void *data) * the header goes into sockaddr. * j1939 may not touch the incoming skb in such way */ - skb = skb_clone(iskb, GFP_ATOMIC); + skb = skb_clone_sk_optional(iskb); if (!skb) return; j1939_priv_get(priv); - can_skb_set_owner(skb, iskb->sk); /* get a pointer to the header of the skb * the skb payload (pointer) is moved, so that the next skb_data diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c index 4e4a510d82f9..c1be6c26ff76 100644 --- a/net/can/j1939/socket.c +++ b/net/can/j1939/socket.c @@ -305,12 +305,11 @@ static void j1939_sk_recv_one(struct j1939_sock *jsk, struct sk_buff *oskb) if (!j1939_sk_recv_match_one(jsk, oskcb)) return; - skb = skb_clone(oskb, GFP_ATOMIC); + skb = skb_clone_sk_optional(oskb); if (!skb) { pr_warn("skb clone failed\n"); return; } - can_skb_set_owner(skb, oskb->sk); skcb = j1939_skb_to_cb(skb); skcb->msg_flags &= ~(MSG_DONTROUTE); diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c index e09d087ba240..e902557bbe17 100644 --- a/net/can/j1939/transport.c +++ b/net/can/j1939/transport.c @@ -1014,12 +1014,10 @@ static int j1939_simple_txnext(struct j1939_session *session) if (!se_skb) return 0; - skb = skb_clone(se_skb, GFP_ATOMIC); + skb = skb_clone_sk_optional(se_skb); if (!skb) return -ENOMEM; - can_skb_set_owner(skb, se_skb->sk); - j1939_tp_set_rxtimeout(session, J1939_SIMPLE_ECHO_TIMEOUT_MS); ret = j1939_send_one(priv, skb);