From nobody Wed Sep 3 01:50:28 2025 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 8D8F2C38145 for ; Fri, 2 Sep 2022 12:32:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236729AbiIBMcP (ORCPT ); Fri, 2 Sep 2022 08:32:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36612 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236566AbiIBMbT (ORCPT ); Fri, 2 Sep 2022 08:31:19 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 159C4E1146; Fri, 2 Sep 2022 05:26:41 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 2F52DB82AA7; Fri, 2 Sep 2022 12:26:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 766CEC433D7; Fri, 2 Sep 2022 12:26:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1662121565; bh=X5zm/3ACRpIb6zzS26kH/5/nDg/MHI/i3VZuY3Du/z8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QF3KZvyayJ1h8bp9xG4K/63DxVQ8ZmsnsTmDL1Fy0Epug1chKPyJ1QixGhzprP9FX AY8GQeq6w1p7oXZg/VIQktKUOs6XRriVqm5kxq41aInSJNsvj/qA8AWGIxU7maEa5e FVF8bw+krJMcCJbkC3n/+B7jQKhlZY+BFKtUQo3o= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Steven Rostedt , Yang Jihong Subject: [PATCH 4.19 49/56] ftrace: Fix NULL pointer dereference in is_ftrace_trampoline when ftrace is dead Date: Fri, 2 Sep 2022 14:19:09 +0200 Message-Id: <20220902121402.128688274@linuxfoundation.org> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20220902121400.219861128@linuxfoundation.org> References: <20220902121400.219861128@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Yang Jihong commit c3b0f72e805f0801f05fa2aa52011c4bfc694c44 upstream. ftrace_startup does not remove ops from ftrace_ops_list when ftrace_startup_enable fails: register_ftrace_function ftrace_startup __register_ftrace_function ... add_ftrace_ops(&ftrace_ops_list, ops) ... ... ftrace_startup_enable // if ftrace failed to modify, ftrace_disabled is= set to 1 ... return 0 // ops is in the ftrace_ops_list. When ftrace_disabled =3D 1, unregister_ftrace_function simply returns witho= ut doing anything: unregister_ftrace_function ftrace_shutdown if (unlikely(ftrace_disabled)) return -ENODEV; // return here, __unregister_ftrace_function i= s not executed, // as a result, ops is still in the ftrace_ops= _list __unregister_ftrace_function ... If ops is dynamically allocated, it will be free later, in this case, is_ftrace_trampoline accesses NULL pointer: is_ftrace_trampoline ftrace_ops_trampoline do_for_each_ftrace_op(op, ftrace_ops_list) // OOPS! op may be NULL! Syzkaller reports as follows: [ 1203.506103] BUG: kernel NULL pointer dereference, address: 0000000000000= 10b [ 1203.508039] #PF: supervisor read access in kernel mode [ 1203.508798] #PF: error_code(0x0000) - not-present page [ 1203.509558] PGD 800000011660b067 P4D 800000011660b067 PUD 130fb8067 PMD 0 [ 1203.510560] Oops: 0000 [#1] SMP KASAN PTI [ 1203.511189] CPU: 6 PID: 29532 Comm: syz-executor.2 Tainted: G B W = 5.10.0 #8 [ 1203.512324] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS = rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 [ 1203.513895] RIP: 0010:is_ftrace_trampoline+0x26/0xb0 [ 1203.514644] Code: ff eb d3 90 41 55 41 54 49 89 fc 55 53 e8 f2 00 fd ff = 48 8b 1d 3b 35 5d 03 e8 e6 00 fd ff 48 8d bb 90 00 00 00 e8 2a 81 26 00 <48= > 8b ab 90 00 00 00 48 85 ed 74 1d e8 c9 00 fd ff 48 8d bb 98 00 [ 1203.518838] RSP: 0018:ffffc900012cf960 EFLAGS: 00010246 [ 1203.520092] RAX: 0000000000000000 RBX: 000000000000007b RCX: ffffffff8a3= 31866 [ 1203.521469] RDX: 0000000000000000 RSI: 0000000000000008 RDI: 00000000000= 0010b [ 1203.522583] RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff8df= 18b07 [ 1203.523550] R10: fffffbfff1be3160 R11: 0000000000000001 R12: 00000000004= 78399 [ 1203.524596] R13: 0000000000000000 R14: ffff888145088000 R15: 00000000000= 00008 [ 1203.525634] FS: 00007f429f5f4700(0000) GS:ffff8881daf00000(0000) knlGS:= 0000000000000000 [ 1203.526801] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1203.527626] CR2: 000000000000010b CR3: 0000000170e1e001 CR4: 00000000003= 706e0 [ 1203.528611] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 00000000000= 00000 [ 1203.529605] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 00000000000= 00400 Therefore, when ftrace_startup_enable fails, we need to rollback registrati= on process and remove ops from ftrace_ops_list. Link: https://lkml.kernel.org/r/20220818032659.56209-1-yangjihong1@huawei.c= om Suggested-by: Steven Rostedt Signed-off-by: Yang Jihong Signed-off-by: Steven Rostedt (Google) Signed-off-by: Greg Kroah-Hartman --- kernel/trace/ftrace.c | 10 ++++++++++ 1 file changed, 10 insertions(+) --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -2748,6 +2748,16 @@ static int ftrace_startup(struct ftrace_ =20 ftrace_startup_enable(command); =20 + /* + * If ftrace is in an undefined state, we just remove ops from list + * to prevent the NULL pointer, instead of totally rolling it back and + * free trampoline, because those actions could cause further damage. + */ + if (unlikely(ftrace_disabled)) { + __unregister_ftrace_function(ops); + return -ENODEV; + } + ops->flags &=3D ~FTRACE_OPS_FL_ADDING; =20 return 0;