Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932256AbVKGQ6w (ORCPT ); Mon, 7 Nov 2005 11:58:52 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932277AbVKGQ6v (ORCPT ); Mon, 7 Nov 2005 11:58:51 -0500 Received: from mail.tv-sign.ru ([213.234.233.51]:48806 "EHLO several.ru") by vger.kernel.org with ESMTP id S932256AbVKGQ6v (ORCPT ); Mon, 7 Nov 2005 11:58:51 -0500 Message-ID: <436F991B.97AFC4C5@tv-sign.ru> Date: Mon, 07 Nov 2005 21:12:43 +0300 From: Oleg Nesterov X-Mailer: Mozilla 4.76 [en] (X11; U; Linux 2.2.20 i686) X-Accept-Language: en MIME-Version: 1.0 To: paulmck@us.ibm.com, Roland McGrath , George Anzinger , akpm@osdl.org, linux-kernel@vger.kernel.org, dipankar@in.ibm.com, mingo@elte.hu, suzannew@cs.pdx.edu, Chris Wright Subject: [PATCH] fix de_thread() vs send_group_sigqueue() race References: <20051105013650.GA17461@us.ibm.com> <436CDEAF.E236BC40@tv-sign.ru> <20051106010004.GB20178@us.ibm.com> <436E1401.920A83EE@tv-sign.ru> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2255 Lines: 67 When non-leader thread does exec, de_thread calls release_task(leader) before calling exit_itimers(). If local timer interrupt happens in between, it can oops in send_group_sigqueue() while taking ->sighand->siglock == NULL. However, we can't change send_group_sigqueue() to check p->signal != NULL, because sys_timer_create() does get_task_struct() only in SIGEV_THREAD_ID case. So it is possible that this task_struct was already freed and we can't trust p->signal. This patch changes de_thread() so that leader released after exit_itimers() call. Signed-off-by: Oleg Nesterov --- 2.6.14/fs/exec.c~ 2005-09-21 21:08:33.000000000 +0400 +++ 2.6.14/fs/exec.c 2005-11-07 23:54:42.000000000 +0300 @@ -593,6 +593,7 @@ static inline int de_thread(struct task_ struct signal_struct *sig = tsk->signal; struct sighand_struct *newsighand, *oldsighand = tsk->sighand; spinlock_t *lock = &oldsighand->siglock; + struct task_struct *leader = NULL; int count; /* @@ -668,7 +669,7 @@ static inline int de_thread(struct task_ * and to assume its PID: */ if (!thread_group_leader(current)) { - struct task_struct *leader = current->group_leader, *parent; + struct task_struct *parent; struct dentry *proc_dentry1, *proc_dentry2; unsigned long exit_state, ptrace; @@ -677,6 +678,7 @@ static inline int de_thread(struct task_ * It should already be zombie at this point, most * of the time. */ + leader = current->group_leader; while (leader->exit_state != EXIT_ZOMBIE) yield(); @@ -736,7 +738,6 @@ static inline int de_thread(struct task_ proc_pid_flush(proc_dentry2); BUG_ON(exit_state != EXIT_ZOMBIE); - release_task(leader); } /* @@ -746,8 +747,11 @@ static inline int de_thread(struct task_ sig->flags = 0; no_thread_group: - BUG_ON(atomic_read(&sig->count) != 1); exit_itimers(sig); + if (leader) + release_task(leader); + + BUG_ON(atomic_read(&sig->count) != 1); if (atomic_read(&oldsighand->count) == 1) { /* - 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/