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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 72D93C3F6B0 for ; Thu, 25 Aug 2022 01:46:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233687AbiHYBqw (ORCPT ); Wed, 24 Aug 2022 21:46:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54456 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236817AbiHYBpt (ORCPT ); Wed, 24 Aug 2022 21:45:49 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E64BE9CCC4; Wed, 24 Aug 2022 18:40:54 -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 341CDB826DA; Thu, 25 Aug 2022 01:40:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 21F88C433D6; Thu, 25 Aug 2022 01:39:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1661391598; bh=wJadzHfZw4n/3J3YYa2f6ZRweztbnt9iAojLQl8CY98=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=b5Q0MPTagX16WsKKkmuWkPrX8XT2oJ0wbilW2/6hpgLBRdH+RT5tAIYRbwUwo2GDJ OeU4PB/7dJaCMCTyX8F0dVOj3yKHyj19od1zQQtdLvIPeA5aUtMrYe64AhPcXKg8Hf nDcIOzhk7i119+BeRNpKshmvn9SQpJTuPH8RYbcAj1KZhYLl/hlKAxYYxCXCdfV+Zf jiiiJa+m9/fbebHQR99fPyNvsHN5s1lqKu59MDPYRA2DdCprPybd1GA/lQtK+meP7L DhwRWx3o47gkT3ejaSC8lWBea2TKG3tyyefC3qH5m8On9PLt9y1rBJeNxUJHuilb9Y 0oniWr4FDZiiw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Yang Jihong , Steven Rostedt , Sasha Levin , mingo@redhat.com Subject: [PATCH AUTOSEL 5.4 8/8] ftrace: Fix NULL pointer dereference in is_ftrace_trampoline when ftrace is dead Date: Wed, 24 Aug 2022 21:39:27 -0400 Message-Id: <20220825013932.23467-8-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220825013932.23467-1-sashal@kernel.org> References: <20220825013932.23467-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yang Jihong [ Upstream commit c3b0f72e805f0801f05fa2aa52011c4bfc694c44 ] 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 = 1, unregister_ftrace_function simply returns without doing anything: unregister_ftrace_function ftrace_shutdown if (unlikely(ftrace_disabled)) return -ENODEV; // return here, __unregister_ftrace_function is 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: 000000000000010b [ 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: ffffffff8a331866 [ 1203.521469] RDX: 0000000000000000 RSI: 0000000000000008 RDI: 000000000000010b [ 1203.522583] RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff8df18b07 [ 1203.523550] R10: fffffbfff1be3160 R11: 0000000000000001 R12: 0000000000478399 [ 1203.524596] R13: 0000000000000000 R14: ffff888145088000 R15: 0000000000000008 [ 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: 00000000003706e0 [ 1203.528611] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 1203.529605] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Therefore, when ftrace_startup_enable fails, we need to rollback registration process and remove ops from ftrace_ops_list. Link: https://lkml.kernel.org/r/20220818032659.56209-1-yangjihong1@huawei.com Suggested-by: Steven Rostedt Signed-off-by: Yang Jihong Signed-off-by: Steven Rostedt (Google) Signed-off-by: Sasha Levin --- kernel/trace/ftrace.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 7719d444bda1..44f1469af842 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -2732,6 +2732,16 @@ int ftrace_startup(struct ftrace_ops *ops, int command) ftrace_startup_enable(command); + /* + * 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 &= ~FTRACE_OPS_FL_ADDING; return 0; -- 2.35.1