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=-9.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,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 022EDC282C0 for ; Fri, 25 Jan 2019 15:11:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BEA33218DE for ; Fri, 25 Jan 2019 15:11:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="XcBS4vE8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727998AbfAYPLP (ORCPT ); Fri, 25 Jan 2019 10:11:15 -0500 Received: from mail-pg1-f195.google.com ([209.85.215.195]:34401 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726265AbfAYPLO (ORCPT ); Fri, 25 Jan 2019 10:11:14 -0500 Received: by mail-pg1-f195.google.com with SMTP id j10so4339409pga.1; Fri, 25 Jan 2019 07:11:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=jok7qk0SvcTErq4QhWTtEyNLN8Pw3lIN4O8wfp69zT0=; b=XcBS4vE8hjCF1kGAzFnAu4mqmThaGJxESEJGmIM8jwdTpbXNmqSifhh/NsJ05umkuS 8PGKdAamavi9PgL1wqp+vsTwtpPwTfYUf2vsnzyYVQes3DWXOlOGTDTI3nXBd5F6Qy8W AJagEpNI7+IlZeWupBNykZJ1nEYDLSwOUb5xrwBQX44MTf+FDjy7VVTFtBpa83tmwP06 1YGAXat+1YRoXPl/DZ6rGA5ieu0dw9Jr3WspfH6gF8y+lkQklIjQkF53KTyiOmNi/H3E BH6RhoEjUm7pZDsj9EeAIh7dFMwy6j1SfiuqDcn1aaUmog7ef7Ow83pFCS0y09tFTQsX FvVw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=jok7qk0SvcTErq4QhWTtEyNLN8Pw3lIN4O8wfp69zT0=; b=O2gguroacg1LaN8JY/mab1547RkD/hYYDUCa6Va+Jsi7Lp/uClrj5b3OBqp57SMqJK +j+IZP8EZUa/9E4MOZ7pTP0wLpd2aogKnTrURUQaYK4kc9WaR/XkwJe/t3MrXjptFzDq tDj3lij5qnnQE3GPVeva+EeddZa4sFg9DlVRjg9iWCMQMjyh5vpLVb3rs+jwYIs+zr4e 4OQi77cwzNayHZMfg81MtsP6b5RgbMSwyDNdwKtA6vi9Ow9BWyn+2OUQ5BrzpSCPigyt XneLjFNN6v39gES15deo4EYLqVTIaNlVwrr+W+Jmv7od6sAN36g6h+7oNB07kQV8Qx/i Avsw== X-Gm-Message-State: AJcUukfvDhM6B+VjXTBtGzFWXXuFiSykFmAdggriMdPF6EkpH/ZfSncT FIz6hkbWXaPugXczdWjOu+g= X-Google-Smtp-Source: ALg8bN5qeoK+xcnoTkGNH9R5r5xQ+fAwGiFYf6i8+Ncjnj+2+BSwi6WPa0Pwdx8Lmeo5EABfYeVFMQ== X-Received: by 2002:a63:151f:: with SMTP id v31mr10130142pgl.34.1548429073902; Fri, 25 Jan 2019 07:11:13 -0800 (PST) Received: from localhost.localdomain ([111.196.19.104]) by smtp.gmail.com with ESMTPSA id 4sm32238097pfq.10.2019.01.25.07.11.11 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 25 Jan 2019 07:11:13 -0800 (PST) From: Changbin Du To: rostedt@goodmis.org Cc: mingo@redhat.com, linux-kernel@vger.kernel.org, Changbin Du , stable@vger.kernel.org Subject: [PATCH] kprobe: safely access memory specified by userspace Date: Fri, 25 Jan 2019 23:10:50 +0800 Message-Id: <20190125151051.7381-1-changbin.du@gmail.com> X-Mailer: git-send-email 2.19.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The userspace can ask kprobe to intercept strings at any memory address, including invalid kernel address. In this case, fetch_store_strlen() would crash since it uses general usercopy function. For example, we can crash the kernel by doing something as below: $ sudo kprobe 'p:do_sys_open +0(+0(%si)):string' [ 103.620391] BUG: GPF in non-whitelisted uaccess (non-canonical address?) [ 103.622104] general protection fault: 0000 [#1] SMP PTI [ 103.623424] CPU: 10 PID: 1046 Comm: cat Not tainted 5.0.0-rc3-00130-gd73aba1-dirty #96 [ 103.625321] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-2-g628b2e6-dirty-20190104_103505-linux 04/01/2014 [ 103.628284] RIP: 0010:process_fetch_insn+0x1ab/0x4b0 [ 103.629518] Code: 10 83 80 28 2e 00 00 01 31 d2 31 ff 48 8b 74 24 28 eb 0c 81 fa ff 0f 00 00 7f 1c 85 c0 75 18 66 66 90 0f ae e8 48 63 ca 89 f8 <8a> 0c 31 66 66 90 83 c2 01 84 c9 75 dc 89 54 24 34 89 44 24 28 48 [ 103.634032] RSP: 0018:ffff88845eb37ce0 EFLAGS: 00010246 [ 103.635312] RAX: 0000000000000000 RBX: ffff888456c4e5a8 RCX: 0000000000000000 [ 103.637057] RDX: 0000000000000000 RSI: 2e646c2f6374652f RDI: 0000000000000000 [ 103.638795] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 [ 103.640556] R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000 [ 103.642297] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 103.644040] FS: 0000000000000000(0000) GS:ffff88846f000000(0000) knlGS:0000000000000000 [ 103.646019] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 103.647436] CR2: 00007ffc79758038 CR3: 0000000463360006 CR4: 0000000000020ee0 [ 103.649147] Call Trace: [ 103.649781] ? sched_clock_cpu+0xc/0xa0 [ 103.650747] ? do_sys_open+0x5/0x220 [ 103.651635] kprobe_trace_func+0x303/0x380 [ 103.652645] ? do_sys_open+0x5/0x220 [ 103.653528] kprobe_dispatcher+0x45/0x50 [ 103.654682] ? do_sys_open+0x1/0x220 [ 103.655875] kprobe_ftrace_handler+0x90/0xf0 [ 103.657282] ftrace_ops_assist_func+0x54/0xf0 [ 103.658564] ? __call_rcu+0x1dc/0x280 [ 103.659482] 0xffffffffc00000bf [ 103.660384] ? __ia32_sys_open+0x20/0x20 [ 103.661682] ? do_sys_open+0x1/0x220 [ 103.662863] do_sys_open+0x5/0x220 [ 103.663988] do_syscall_64+0x60/0x210 [ 103.665201] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 103.666862] RIP: 0033:0x7fc22fadccdd [ 103.668034] Code: 48 89 54 24 e0 41 83 e2 40 75 32 89 f0 25 00 00 41 00 3d 00 00 41 00 74 24 89 f2 b8 01 01 00 00 48 89 fe bf 9c ff ff ff 0f 05 <48> 3d 00 f0 ff ff 77 33 f3 c3 66 0f 1f 84 00 00 00 00 00 48 8d 44 [ 103.674029] RSP: 002b:00007ffc7972c3a8 EFLAGS: 00000287 ORIG_RAX: 0000000000000101 [ 103.676512] RAX: ffffffffffffffda RBX: 0000562f86147a21 RCX: 00007fc22fadccdd [ 103.678853] RDX: 0000000000080000 RSI: 00007fc22fae1428 RDI: 00000000ffffff9c [ 103.681151] RBP: ffffffffffffffff R08: 0000000000000000 R09: 0000000000000000 [ 103.683489] R10: 0000000000000000 R11: 0000000000000287 R12: 00007fc22fce90a8 [ 103.685774] R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000 [ 103.688056] Modules linked in: [ 103.689131] ---[ end trace 43792035c28984a1 ]--- This can be fixed by using probe_mem_read() instead. Signed-off-by: Changbin Du Cc: stable@vger.kernel.org --- kernel/trace/trace_kprobe.c | 10 +--------- 1 file changed, 1 insertion(+), 9 deletions(-) diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index d5fb09ebba8b..9eaf07f99212 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -861,22 +861,14 @@ static const struct file_operations kprobe_profile_ops = { static nokprobe_inline int fetch_store_strlen(unsigned long addr) { - mm_segment_t old_fs; int ret, len = 0; u8 c; - old_fs = get_fs(); - set_fs(KERNEL_DS); - pagefault_disable(); - do { - ret = __copy_from_user_inatomic(&c, (u8 *)addr + len, 1); + ret = probe_mem_read(&c, (u8 *)addr + len, 1); len++; } while (c && ret == 0 && len < MAX_STRING_SIZE); - pagefault_enable(); - set_fs(old_fs); - return (ret < 0) ? ret : len; } -- 2.19.1