From patchwork Mon Sep 4 22:11:54 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Olivier L'Heureux X-Patchwork-Id: 720217 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BA934C83F33 for ; Mon, 4 Sep 2023 22:12:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240542AbjIDWMJ (ORCPT ); Mon, 4 Sep 2023 18:12:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37326 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229561AbjIDWMI (ORCPT ); Mon, 4 Sep 2023 18:12:08 -0400 Received: from mail-ej1-x632.google.com (mail-ej1-x632.google.com [IPv6:2a00:1450:4864:20::632]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CACB8CDA for ; Mon, 4 Sep 2023 15:12:03 -0700 (PDT) Received: by mail-ej1-x632.google.com with SMTP id a640c23a62f3a-9a1de3417acso593221266b.0 for ; Mon, 04 Sep 2023 15:12:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mind.be; s=google; t=1693865522; x=1694470322; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=gArWs5Q5c1PsBa7PCApkxjz+wZ4/Au6Fx4OqD6X/u4U=; b=gote8BAH1dfry79ayUQUZp6/WJMCaNkkdJXsd4qoWFaWWiTsgylOK/iI+5K0apMzky HqNaG3WPM425tZJGFaqVr5iBI/BGxc3Z0XKPSvGyDnjQ3aZ5Oh/7sVQMpnEaFA+ffsSO WPF/HRzar9GFtOsecuU4+NwGt0I6MH+6770iZYvCLeTZtri9fO+OY0EzpMOVylFL5hRK a1ipqBmGro2yZBzAOLgCxRhvisICF1apxxF7q2sZ0UXtc1RUxbsPepKsrTFvZ2KHahMT jbhRkFHQlGCChNqQrw2gMs0RUBdkdVc3aM1I5TFNNDYti9rSXooiaLBHu38bA38L/Ykb pj/w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1693865522; x=1694470322; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=gArWs5Q5c1PsBa7PCApkxjz+wZ4/Au6Fx4OqD6X/u4U=; b=USaRazkNKxcl6vgoxyYNs5rpy3ceJPfInlq8HjVQD4O0GzVqmP3yPrfylHmkHkStzC cWQkJ+cmPM7pzfQbrwYd69TCrXJZayRp7tA1ZCXVbKIUIjr+z8wpRSmYhO4effDPb1DL 2dNTwXV4rNRRcvnZggVh7VJ17e4csebYzh95UW8n+6/NaOb4I9vL+y/EY7WriqEbf/Gt r9LRhQQ2TYd04cKxP3/f7vx/QEFiXwnLYDohl2wF+h9wHf/Byo2htFGCiKfGnkgjcG0z B3GtAJ4miB0S6kjwYPxqETZCg/plIJbBaqOVMSIZjKIxai5Tt1MYKc/XzQvxd9iwIaLU DWmw== X-Gm-Message-State: AOJu0YxmQ8aktHSMCjGK0y/b4f54GMtb8PzAD7hcb49fc67JWOAiX6sU PTB4J7BhIljwi0vkPGTyQwck0w== X-Google-Smtp-Source: AGHT+IFaVoPIsdEXXEJGSK0ibzOr6EUvtMfDzXMWWIs50iC+huwvFJoVXIvugNjIAkxZWWVCqFSLpQ== X-Received: by 2002:a17:906:3010:b0:9a5:bceb:1cf8 with SMTP id 16-20020a170906301000b009a5bceb1cf8mr11138985ejz.3.1693865522265; Mon, 04 Sep 2023 15:12:02 -0700 (PDT) Received: from olheureu-ThinkPad-E560.local.ess-mail.com ([2a02:578:85b9:1300:6c89:e61f:b837:7d81]) by smtp.gmail.com with ESMTPSA id z16-20020a170906715000b00993cc1242d4sm6692673ejj.151.2023.09.04.15.12.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 Sep 2023 15:12:01 -0700 (PDT) From: Olivier L'Heureux To: Marcel Holtmann , Johan Hedberg , Luiz Augusto von Dentz Cc: linux-bluetooth@vger.kernel.org, Olivier L'Heureux Subject: [PATCH 3/7] Bluetooth: L2CAP: use refcount on struct l2cap_chan->conn Date: Tue, 5 Sep 2023 00:11:54 +0200 Message-Id: <20230904221158.35425-4-olivier.lheureux@mind.be> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230904221158.35425-1-olivier.lheureux@mind.be> References: <20230904221158.35425-1-olivier.lheureux@mind.be> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-bluetooth@vger.kernel.org We have detected a memory leak of "struct l2cap_conn" objects, and of "struct hci_conn" in the bluetooth subsystem [12]. The second is a consequence of the first. This memory leak was also detected by syzbot [13]. "struct l2cap_conn" is allocated in "l2cap_conn_add()" [2]. "struct l2cap_conn" is reference-counted [1] by its "ref" member [3]: every holder of a reference to it should increment the reference counter by calling "l2cap_conn_get()" [4], and every reference holder that stops keeping the reference should call "l2cap_conn_put()" [5]. The "struct l2cap_conn" is freed when the counter reaches 0, meaning there is no reference holder any more. This mechanism is already used by the "hidp_session_new()" [6] and "session_free()" [7] functions that create and delete the "struct hidp_session" [8] objects, which contains a "conn" reference to a "struct l2cap_conn". The same reference counting mechanism is not used for the "conn" reference kept in the "struct l2cap_chan" [9] object. There were two places where the reference counting was not applied: 1. In "__l2cap_chan_add()" [11], the "struct l2cap_conn" reference is stored in the "conn" member of the "struct l2cap_chan" [9]. 2. In "l2cap_chan_del()" [10], the "conn" member of the "struct l2cap_chan" is set to NULL. To apply the reference counting to the "conn" member of the "struct l2cap_chan", we use "l2cap_conn_get()" in "__l2cap_chan_add()", where we store the reference, and "l2cap_conn_put()" in "l2cap_chan_del()", where we drop the reference. Handling the "conn" member of the "struct l2cap_chan" with the existing reference counter will help to fix the kernel memory leak in a following commit. References: - [1] "Adding reference counters (krefs) to kernel objects" - [2] "l2cap_conn_add()" - [3] "struct l2cap_conn" - [4] "l2cap_conn_get()" - [5] "l2cap_conn_put()" - [6] "hidp_session_new()" - [7] "session_free()" - [8] "struct hidp_session" - [9] "struct l2cap_chan" - [10] "l2cap_chan_del()" - [11] "__l2cap_chan_add()" - [12] "ble-memleak-repro" - [13] "[syzbot] [bluetooth?] memory leak in hci_conn_add (2)" Signed-off-by: Olivier L'Heureux Signed-off-by: Olivier L'Heureux --- net/bluetooth/l2cap_core.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index c749b434df97..768632fba6f8 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -587,7 +587,7 @@ void __l2cap_chan_add(struct l2cap_conn *conn, struct l2cap_chan *chan) conn->disc_reason = HCI_ERROR_REMOTE_USER_TERM; - chan->conn = conn; + chan->conn = l2cap_conn_get(conn); switch (chan->chan_type) { case L2CAP_CHAN_CONN_ORIENTED: @@ -669,6 +669,8 @@ void l2cap_chan_del(struct l2cap_chan *chan, int err) if (mgr && mgr->bredr_chan == chan) mgr->bredr_chan = NULL; + + l2cap_conn_put(conn); } if (chan->hs_hchan) {