From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763270AbZEFWNK (ORCPT ); Wed, 6 May 2009 18:13:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760657AbZEFVzE (ORCPT ); Wed, 6 May 2009 17:55:04 -0400 Received: from kroah.org ([198.145.64.141]:57318 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761525AbZEFVy5 (ORCPT ); Wed, 6 May 2009 17:54:57 -0400 X-Mailbox-Line: From gregkh@mini.kroah.org Wed May 6 14:48:01 2009 Message-Id: <20090506214801.282196228@mini.kroah.org> User-Agent: quilt/0.48-1 Date: Wed, 06 May 2009 14:46:11 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: Justin Forbes , Zwane Mwaikambo , "Theodore Ts'o" , Randy Dunlap , Dave Jones , Chuck Wolber , Chris Wedgwood , Michael Krufky , Chuck Ebbert , Domenico Andreoli , Willy Tarreau , Rodrigo Rubira Branco , Jake Edge , Eugene Teo , torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Oleg Nesterov , Roland McGrath , Hugh Dickins Subject: [patch 43/58] check_unsafe_exec: s/lock_task_sighand/rcu_read_lock/ References: <20090506214528.660389067@mini.kroah.org> Content-Disposition: inline; filename=check_unsafe_exec-s-lock_task_sighand-rcu_read_lock.patch In-Reply-To: <20090506215017.GA21981@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.29-stable review patch. If anyone has any objections, please let us know. ------------------ From: Oleg Nesterov commit 437f7fdb607f32b737e4da9f14bebcfdac2c90c3 upstream. write_lock(¤t->fs->lock) guarantees we can't wrongly miss LSM_UNSAFE_SHARE, this is what we care about. Use rcu_read_lock() instead of ->siglock to iterate over the sub-threads. We must see all CLONE_THREAD|CLONE_FS threads which didn't pass exit_fs(), it takes fs->lock too. With or without this patch we can miss the freshly cloned thread and set LSM_UNSAFE_SHARE, we don't care. Signed-off-by: Oleg Nesterov Acked-by: Roland McGrath [ Fixed lock/unlock typo - Hugh ] Acked-by: Hugh Dickins Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/exec.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) --- a/fs/exec.c +++ b/fs/exec.c @@ -1052,7 +1052,6 @@ EXPORT_SYMBOL(install_exec_creds); int check_unsafe_exec(struct linux_binprm *bprm) { struct task_struct *p = current, *t; - unsigned long flags; unsigned n_fs; int res = 0; @@ -1060,11 +1059,12 @@ int check_unsafe_exec(struct linux_binpr n_fs = 1; write_lock(&p->fs->lock); - lock_task_sighand(p, &flags); + rcu_read_lock(); for (t = next_thread(p); t != p; t = next_thread(t)) { if (t->fs == p->fs) n_fs++; } + rcu_read_unlock(); if (p->fs->users > n_fs) { bprm->unsafe |= LSM_UNSAFE_SHARE; @@ -1075,8 +1075,6 @@ int check_unsafe_exec(struct linux_binpr res = 1; } } - - unlock_task_sighand(p, &flags); write_unlock(&p->fs->lock); return res;