From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754669Ab3HKR7F (ORCPT ); Sun, 11 Aug 2013 13:59:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:22440 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754331Ab3HKR7C (ORCPT ); Sun, 11 Aug 2013 13:59:02 -0400 Date: Sun, 11 Aug 2013 19:53:25 +0200 From: Oleg Nesterov To: Andrew Morton Cc: Al Viro , Andy Lutomirski , Ben Woodard , "Eric W. Biederman" , Mark Grondona , linux-kernel@vger.kernel.org Subject: [PATCH] __ptrace_may_access() should not deny sub-threads Message-ID: <20130811175325.GA12587@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mark Grondona __ptrace_may_access() checks get_dumpable/ptrace_has_cap/etc if task != current, this can can lead to surprising results. For example, a sub-thread can't readlink("/proc/self/exe") if the executable is not readable. setup_new_exec()->would_dump() notices that inode_permission(MAY_READ) fails and then it does set_dumpable(suid_dumpable). After that get_dumpable() fails. (It is not clear why proc_pid_readlink() checks get_dumpable(), perhaps we could add PTRACE_MODE_NODUMPABLE) Change __ptrace_may_access() to use same_thread_group() instead of "task == current". Any security check is pointless when the tasks share the same ->mm. Signed-off-by: Mark Grondona Signed-off-by: Ben Woodard Signed-off-by: Oleg Nesterov --- kernel/ptrace.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/kernel/ptrace.c b/kernel/ptrace.c index a146ee3..dd562e9 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -236,7 +236,7 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode) */ int dumpable = 0; /* Don't let security modules deny introspection */ - if (task == current) + if (same_thread_group(task, current)) return 0; rcu_read_lock(); tcred = __task_cred(task); -- 1.5.5.1