From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756658Ab3IKRUi (ORCPT ); Wed, 11 Sep 2013 13:20:38 -0400 Received: from mx1.redhat.com ([209.132.183.28]:31813 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756232Ab3IKRUg (ORCPT ); Wed, 11 Sep 2013 13:20:36 -0400 Date: Wed, 11 Sep 2013 19:14:03 +0200 From: Oleg Nesterov To: Andrew Morton Cc: Andy Lutomirski , Brad Spengler , "Eric W. Biederman" , Willy Tarreau , linux-kernel@vger.kernel.org Subject: [PATCH v2 1/1] proc: make proc_fd_permission() thread-friendly Message-ID: <20130911171403.GA15381@redhat.com> References: <20130911171341.GA15371@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130911171341.GA15371@redhat.com> 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 proc_fd_permission() says "process can still access /proc/self/fd after it has executed a setuid()", but the "task_pid() = proc_pid() check only helps if the task is group leader, /proc/self points to /proc/. Change this check to use task_tgid() so that the whole thread group can access its /proc/self/fd or /proc//fd. Notes: - CLONE_THREAD does not require CLONE_FILES so task->files can differ, but I don't think this can lead to any security problem. And this matches same_thread_group() in __ptrace_may_access(). - /proc/self should probably point to /proc/, but it is too late to change the rules. Perhaps it makes sense to add /proc/thread though. Test-case: void *tfunc(void *arg) { assert(opendir("/proc/self/fd")); return NULL; } int main(void) { pthread_t t; pthread_create(&t, NULL, tfunc, NULL); pthread_join(t, NULL); return 0; } fails if, say, this executable is not readable and suid_dumpable = 0. Signed-off-by: Oleg Nesterov --- fs/proc/fd.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/fs/proc/fd.c b/fs/proc/fd.c index 0ff80f9..985ea88 100644 --- a/fs/proc/fd.c +++ b/fs/proc/fd.c @@ -286,7 +286,7 @@ int proc_fd_permission(struct inode *inode, int mask) int rv = generic_permission(inode, mask); if (rv == 0) return 0; - if (task_pid(current) == proc_pid(inode)) + if (task_tgid(current) == proc_pid(inode)) rv = 0; return rv; } -- 1.5.5.1