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[2620:137:e000::1:20]) by mx.google.com with ESMTP id o7-20020a170902bcc700b001991d9a1127si1309935pls.579.2023.03.16.22.34.54; Thu, 16 Mar 2023 22:35:08 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@mediatek.com header.s=dk header.b=GuP51zBd; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=mediatek.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229494AbjCQFbY (ORCPT + 99 others); Fri, 17 Mar 2023 01:31:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56858 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229621AbjCQFbW (ORCPT ); Fri, 17 Mar 2023 01:31:22 -0400 Received: from mailgw01.mediatek.com (unknown [60.244.123.138]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CAE53B5A99; Thu, 16 Mar 2023 22:31:19 -0700 (PDT) X-UUID: efadbe02c48411ed91027fb02e0f1d65-20230317 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=mediatek.com; s=dk; h=Content-Type:MIME-Version:Message-ID:Date:Subject:CC:To:From; bh=B0oWSAqYH3d4rxQTXEiSY0Y15GtFNYgYD2YcLGwJd3A=; b=GuP51zBdOowuCYrz23UP0QbVtjheq+3uxCfc+GvMA7tA+fwHwfFNmsmFLxJe9uSmeSoVDl9uVhfodJmIG4GO1SoH7cnG/uE3exX19rwr/JbdYmGpvO+dxYCo5TU50JX+qu1+TK6UpKutcw68u/t9PzKpUbjn6mtP/U/MD+XGwg8=; X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.1.21,REQID:5c0186f2-fe5c-4f3a-b22c-fd3d2e832211,IP:0,U RL:0,TC:0,Content:-5,EDM:0,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTION :release,TS:-5 X-CID-META: VersionHash:83295aa,CLOUDID:c98b87b3-beed-4dfc-bd9c-e1b22fa6ccc4,B ulkID:nil,BulkQuantity:0,Recheck:0,SF:102,TC:nil,Content:0,EDM:-3,IP:nil,U RL:11|1,File:nil,Bulk:nil,QS:nil,BEC:nil,COL:0,OSI:0,OSA:0,AV:0 X-CID-BVR: 0 X-CID-BAS: 0,_,0,_ X-UUID: efadbe02c48411ed91027fb02e0f1d65-20230317 Received: from mtkmbs10n2.mediatek.inc [(172.21.101.183)] by mailgw01.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-GCM-SHA384 256/256) with ESMTP id 784308367; Fri, 17 Mar 2023 13:31:15 +0800 Received: from mtkmbs13n1.mediatek.inc (172.21.101.193) by mtkmbs10n2.mediatek.inc (172.21.101.183) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.25; Fri, 17 Mar 2023 13:31:14 +0800 Received: from mtksdccf07.mediatek.inc (172.21.84.99) by mtkmbs13n1.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.2.1118.25 via Frontend Transport; Fri, 17 Mar 2023 13:31:14 +0800 From: Cheng-Jui Wang To: Steven Rostedt , Masami Hiramatsu , Matthias Brugger , AngeloGioacchino Del Regno , "Tom Zanussi" CC: , , Tze-nan Wu , , , , , Subject: [PATCH] tracing: Fix use-after-free and double-free on last_cmd Date: Fri, 17 Mar 2023 13:30:44 +0800 Message-ID: <20230317053044.13828-1-cheng-jui.wang@mediatek.com> X-Mailer: git-send-email 2.18.0 MIME-Version: 1.0 X-MTK: N X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_MSPIKE_H2,SPF_HELO_PASS, SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1760591933921066008?= X-GMAIL-MSGID: =?utf-8?q?1760591933921066008?= From: "Tze-nan Wu" Currently, the last_cmd variable can be accessed by multiple processes asynchronously when multiple users manipulate synthetic_events node at the same time, it could lead to use-after-free or double-free. This patch add lastcmd_mutex to prevent last_cmd from being accessed asynchronously. ================================================================ It's easy to reproduce in the KASAN environment by running the two scripts below in different shells. script 1: while : do echo -n -e '\x88' > /sys/kernel/tracing/synthetic_events done script 2: while : do echo -n -e '\xb0' > /sys/kernel/tracing/synthetic_events done ================================================================ double-free scenario: process A process B ------------------- --------------- 1.kstrdup last_cmd 2.free last_cmd 3.free last_cmd(double-free) ================================================================ use-after-free scenario: process A process B ------------------- --------------- 1.kstrdup last_cmd 2.free last_cmd 3.tracing_log_err(use-after-free) ================================================================ Appendix 1. KASAN report double-free: BUG: KASAN: double-free in kfree+0xdc/0x1d4 Free of addr ***** by task sh/4879 Call trace: ... kfree+0xdc/0x1d4 create_or_delete_synth_event+0x60/0x1e8 trace_parse_run_command+0x2bc/0x4b8 synth_events_write+0x20/0x30 vfs_write+0x200/0x830 ... Allocated by task 4879: ... kstrdup+0x5c/0x98 create_or_delete_synth_event+0x6c/0x1e8 trace_parse_run_command+0x2bc/0x4b8 synth_events_write+0x20/0x30 vfs_write+0x200/0x830 ... Freed by task 5464: ... kfree+0xdc/0x1d4 create_or_delete_synth_event+0x60/0x1e8 trace_parse_run_command+0x2bc/0x4b8 synth_events_write+0x20/0x30 vfs_write+0x200/0x830 ... ================================================================ Appendix 2. KASAN report use-after-free: BUG: KASAN: use-after-free in strlen+0x5c/0x7c Read of size 1 at addr ***** by task sh/5483 sh: CPU: 7 PID: 5483 Comm: sh ... __asan_report_load1_noabort+0x34/0x44 strlen+0x5c/0x7c tracing_log_err+0x60/0x444 create_or_delete_synth_event+0xc4/0x204 trace_parse_run_command+0x2bc/0x4b8 synth_events_write+0x20/0x30 vfs_write+0x200/0x830 ... Allocated by task 5483: ... kstrdup+0x5c/0x98 create_or_delete_synth_event+0x80/0x204 trace_parse_run_command+0x2bc/0x4b8 synth_events_write+0x20/0x30 vfs_write+0x200/0x830 ... Freed by task 5480: ... kfree+0xdc/0x1d4 create_or_delete_synth_event+0x74/0x204 trace_parse_run_command+0x2bc/0x4b8 synth_events_write+0x20/0x30 vfs_write+0x200/0x830 ... Fixes: 27c888da9867 ("tracing: Remove size restriction on synthetic event cmd error logging") Cc: stable@vger.kernel.org Signed-off-by: Tze-nan Wu --- kernel/trace/trace_events_synth.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c index 46d0abb32d0f..ce438eccab2e 100644 --- a/kernel/trace/trace_events_synth.c +++ b/kernel/trace/trace_events_synth.c @@ -42,16 +42,25 @@ enum { ERRORS }; #undef C #define C(a, b) b +static DEFINE_MUTEX(lastcmd_mutex); + static const char *err_text[] = { ERRORS }; static char *last_cmd; static int errpos(const char *str) { - if (!str || !last_cmd) - return 0; + int ret = 0; + + mutex_lock(&lastcmd_mutex); + if (!str || !last_cmd) { + mutex_unlock(&lastcmd_mutex); + return ret; + } - return err_pos(last_cmd, str); + ret = err_pos(last_cmd, str); + mutex_unlock(&lastcmd_mutex); + return ret; } static void last_cmd_set(const char *str) @@ -59,18 +68,24 @@ static void last_cmd_set(const char *str) if (!str) return; + mutex_lock(&lastcmd_mutex); kfree(last_cmd); last_cmd = kstrdup(str, GFP_KERNEL); + mutex_unlock(&lastcmd_mutex); } static void synth_err(u8 err_type, u16 err_pos) { - if (!last_cmd) + mutex_lock(&lastcmd_mutex); + if (!last_cmd) { + mutex_unlock(&lastcmd_mutex); return; + } tracing_log_err(NULL, "synthetic_events", last_cmd, err_text, err_type, err_pos); + mutex_unlock(&lastcmd_mutex); } static int create_synth_event(const char *raw_command);