From patchwork Tue Nov 17 13:04:45 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 328058 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=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, 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 60EF0C64E7C for ; Tue, 17 Nov 2020 13:59:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0B096206F1 for ; Tue, 17 Nov 2020 13:59:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="yyFtZ9rL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730047AbgKQNRv (ORCPT ); Tue, 17 Nov 2020 08:17:51 -0500 Received: from mail.kernel.org ([198.145.29.99]:50270 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730600AbgKQNRu (ORCPT ); Tue, 17 Nov 2020 08:17:50 -0500 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 11DAA241A6; Tue, 17 Nov 2020 13:17:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605619069; bh=yU/BCde+VQPfwl4DfTOEL7nAzesvlkrIGSOGDzKVqPo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yyFtZ9rLnwMLZRfiuAly8Tq624tALYJx6DWD6pBgA3Y3R4x39D1FtJt2TqlgAbMEA Cxk1r2yHCRy9VmeTWTMJdVWpj5/q2C6n6AtqXhNwbcn5BXgnfJrSmrIZxp7zfxJoGg kCEM7Fg+tOLFm1xqO5AjqaRm3bApHMLF3dAv0Sis= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Oleksij Rempel , Oliver Hartkopp , Marc Kleine-Budde , Sasha Levin Subject: [PATCH 4.19 018/101] can: can_create_echo_skb(): fix echo skb generation: always use skb_clone() Date: Tue, 17 Nov 2020 14:04:45 +0100 Message-Id: <20201117122113.977504749@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201117122113.128215851@linuxfoundation.org> References: <20201117122113.128215851@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Oleksij Rempel [ Upstream commit 286228d382ba6320f04fa2e7c6fc8d4d92e428f4 ] All user space generated SKBs are owned by a socket (unless injected into the key via AF_PACKET). If a socket is closed, all associated skbs will be cleaned up. This leads to a problem when a CAN driver calls can_put_echo_skb() on a unshared SKB. If the socket is closed prior to the TX complete handler, can_get_echo_skb() and the subsequent delivering of the echo SKB to all registered callbacks, a SKB with a refcount of 0 is delivered. To avoid the problem, in can_get_echo_skb() the original SKB is now always cloned, regardless of shared SKB or not. If the process exists it can now safely discard its SKBs, without disturbing the delivery of the echo SKB. The problem shows up in the j1939 stack, when it clones the incoming skb, which detects the already 0 refcount. We can easily reproduce this with following example: testj1939 -B -r can0: & cansend can0 1823ff40#0123 WARNING: CPU: 0 PID: 293 at lib/refcount.c:25 refcount_warn_saturate+0x108/0x174 refcount_t: addition on 0; use-after-free. Modules linked in: coda_vpu imx_vdoa videobuf2_vmalloc dw_hdmi_ahb_audio vcan CPU: 0 PID: 293 Comm: cansend Not tainted 5.5.0-rc6-00376-g9e20dcb7040d #1 Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree) Backtrace: [] (dump_backtrace) from [] (show_stack+0x20/0x24) [] (show_stack) from [] (dump_stack+0x8c/0xa0) [] (dump_stack) from [] (__warn+0xe0/0x108) [] (__warn) from [] (warn_slowpath_fmt+0xa8/0xcc) [] (warn_slowpath_fmt) from [] (refcount_warn_saturate+0x108/0x174) [] (refcount_warn_saturate) from [] (j1939_can_recv+0x20c/0x210) [] (j1939_can_recv) from [] (can_rcv_filter+0xb4/0x268) [] (can_rcv_filter) from [] (can_receive+0xb0/0xe4) [] (can_receive) from [] (can_rcv+0x48/0x98) [] (can_rcv) from [] (__netif_receive_skb_one_core+0x64/0x88) [] (__netif_receive_skb_one_core) from [] (__netif_receive_skb+0x38/0x94) [] (__netif_receive_skb) from [] (netif_receive_skb_internal+0x64/0xf8) [] (netif_receive_skb_internal) from [] (netif_receive_skb+0x34/0x19c) [] (netif_receive_skb) from [] (can_rx_offload_napi_poll+0x58/0xb4) Fixes: 0ae89beb283a ("can: add destructor for self generated skbs") Signed-off-by: Oleksij Rempel Link: http://lore.kernel.org/r/20200124132656.22156-1-o.rempel@pengutronix.de Acked-by: Oliver Hartkopp Signed-off-by: Marc Kleine-Budde Signed-off-by: Sasha Levin --- include/linux/can/skb.h | 20 ++++++++------------ 1 file changed, 8 insertions(+), 12 deletions(-) diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h index b3379a97245c1..a34694e675c9a 100644 --- a/include/linux/can/skb.h +++ b/include/linux/can/skb.h @@ -61,21 +61,17 @@ static inline void can_skb_set_owner(struct sk_buff *skb, struct sock *sk) */ static inline struct sk_buff *can_create_echo_skb(struct sk_buff *skb) { - if (skb_shared(skb)) { - struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC); + struct sk_buff *nskb; - if (likely(nskb)) { - can_skb_set_owner(nskb, skb->sk); - consume_skb(skb); - return nskb; - } else { - kfree_skb(skb); - return NULL; - } + nskb = skb_clone(skb, GFP_ATOMIC); + if (unlikely(!nskb)) { + kfree_skb(skb); + return NULL; } - /* we can assume to have an unshared skb with proper owner */ - return skb; + can_skb_set_owner(nskb, skb->sk); + consume_skb(skb); + return nskb; } #endif /* !_CAN_SKB_H */