Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754835AbYCPPvn (ORCPT ); Sun, 16 Mar 2008 11:51:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753304AbYCPPuh (ORCPT ); Sun, 16 Mar 2008 11:50:37 -0400 Received: from x346.tv-sign.ru ([89.108.83.215]:35768 "EHLO mail.screens.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752522AbYCPPug (ORCPT ); Sun, 16 Mar 2008 11:50:36 -0400 Date: Sun, 16 Mar 2008 18:54:55 +0300 From: Oleg Nesterov To: Andrew Morton Cc: Davide Libenzi , "Eric W. Biederman" , Ingo Molnar , Laurent Riffard , Pavel Emelyanov , Roland McGrath , linux-kernel@vger.kernel.org Subject: [PATCH 5/5] ptrace: it is fun to strace /sbin/init Message-ID: <20080316155455.GA20848@tv-sign.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2361 Lines: 71 Ptracing of /sbin/init is not allowed. Of course, this is very dangerous, but may be useful. Introduce the kernel boot parameter to allow this. Note that it is really dangerous, also because init can lose SIGNAL_UNKILLABLE flag. But this is because we are not careful enough with setting signal->flags, this should be cleanuped anyway. Unless I missed something, ptrace_get_task_struct() is pointless. It does not need to check "pid == 1", ptrace_attach() does this. It doesn't need tasklist. It should be replaced with the generic find_get_task_by_vpid() which does not exist yet. Signed-off-by: Oleg Nesterov --- 25/kernel/ptrace.c~5_INIT_PTRACE 2008-03-16 17:22:04.000000000 +0300 +++ 25/kernel/ptrace.c 2008-03-16 18:33:02.000000000 +0300 @@ -160,6 +160,15 @@ int ptrace_may_attach(struct task_struct return !err; } +static int allow_ptrace_init; + +static int __init __allow_ptrace_init(char *str) +{ + allow_ptrace_init = 1; + return 1; +} +__setup("init_ptrace", __allow_ptrace_init); + int ptrace_attach(struct task_struct *task) { int retval; @@ -168,7 +177,7 @@ int ptrace_attach(struct task_struct *ta audit_ptrace(task); retval = -EPERM; - if (task->pid <= 1) + if (unlikely(is_global_init(task)) && likely(!allow_ptrace_init)) goto out; if (same_thread_group(task, current)) goto out; @@ -518,12 +527,6 @@ struct task_struct *ptrace_get_task_stru { struct task_struct *child; - /* - * Tracing init is not allowed. - */ - if (pid == 1) - return ERR_PTR(-EPERM); - read_lock(&tasklist_lock); child = find_task_by_vpid(pid); if (child) --- 25/Documentation/kernel-parameters.txt~5_INIT_PTRACE 2008-02-15 16:58:12.000000000 +0300 +++ 25/Documentation/kernel-parameters.txt 2008-03-16 18:30:28.000000000 +0300 @@ -803,6 +803,8 @@ and is between 256 and 4096 characters. Run specified binary instead of /sbin/init as init process. + init_ptrace [KNL] Allows to ptrace init. Very dangerous. Don't use. + initcall_debug [KNL] Trace initcalls as they are executed. Useful for working out where the kernel is dying during startup. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/