linux-kernel - [PATCH 5/5] ptrace: it is fun to strace /sbin/init

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20080316155455.GA20848@tv-sign.ru>
Date:	Sun, 16 Mar 2008 18:54:55 +0300
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Davide Libenzi <davidel@...ilserver.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Ingo Molnar <mingo@...e.hu>,
	Laurent Riffard <laurent.riffard@...e.fr>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 5/5] ptrace: it is fun to strace /sbin/init

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 <oleg@...sign.ru>

--- 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@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/